We had some similar problems, although not as often or for as long a time period. Have you consulted your pediatrician? Sounds like he has reflux, or allergies, or something wrong that doesn't let him physically sleep long, or get into a good REM cycle or something.
Or he could actually be hungry - have you talked to a few different lactation consultants about his latch? If he has a tongue or lip tie, he might not be removing milk very efficietly, and you might get this kind of nursing pattern. We had trouble with that. Surgery helped immensely. Getting my son's lip and tongue tie fixed might be the best medical decision I've made for him so far.
Might try switching him over from snacking to long meals at the breast - if he doesn't get a good feeding of hind milk, he may not sleep as soundly - this could be what's going on. It takes a while for the hind milk to start, and if he doesn't nurse long enough per feeding he won't get it, and that plus hormones are what make babies sleepy after nursing. If he's a year old, he won't like not having free access whenever he wants it (how dare you change the rules of the game!), but he's probably also eating other food, and would probably adjust just fine once he stops being mad and pitching fits about it. During the day, might try distracting him with fun games and such - our son naturally spaced himself out because he had all sorts of other things he was busy doing. Assuming that you've tried all these suggestions, and talked to the doctor, and he's fine, here's what worked for us:
First he slept on my chest as a newborn baby, because that was absolutely the only way either of us could get any sleep. I didn't sleep very deeply while sleeping w/him because I was constantly aware of him, and I made the space as safe as possible. This lasted for a month or so. We discovered the bassinet we had moved when we laid him into it, and that's what kept waking him up. He hated his sleeping surface to move. Funny thing was, if we put him in the baby swing (at our wits end), usually he would eventually fall asleep. I don't know what the difference was. After the chest period, he slept in a co-sleeper placed on top of our bed (it had hard sides, but an open bottom, so I could lay my hand next to/on him, and he wasn't rolling over yet. ALso we put up a rail on the side of the bed where he was, just in case, so he was hemmed in and couldn't roll or wiggle off. No covers around him or pillows, etc.) Around 2-3 months we introuced a paci along with the co-sleeper, because I'd tried everything else - he wasn't hungry, just wanted to suck, and got mad when the milk came out, and couldn't soothe himself very well. The paci helped him a lot as far as soothing himself goes. We went through 3-4 varieties of paci as he grew before finding one that didn't distort his suck for breastfeeding. He would wake to nurse 2-3 times a night or so through 10 months of age.
Around 6-8 months or so, my husband was tired of sleeping on the couch and wanted his bed back, and baby was still waking a few times a night to nurse. I was getting almost enough sleep. We put a recliner in the baby's room, and I would nurse in that. Transfer to the crib was always a challenge - I found there was an optimal time for it. If I waited twenty minutes after he had fallen asleep at the breast, I could usually put him down w/out him waking. If I waited 10 or 30 minutes, he would wake back up, so I had to make sure I mysef didn't fall asleep and miss the window. I changed and swaddled him before I nursed, so all I had to do was place him in the crib once he fell asleep. Loved those Halo Sleep Sack swaddles and the other regular swaddles with velcro. I could tell by his breathing most of the time when he had entered the sleep state where he was ready. Sometimes I recruited Dad when the transfer didn't work and I was out of patience/sleep deprived - baby definately had less trouble with Dad putting him down and leaving than with me doing it, but there was still crying. We always kept lights low and didn't talk much to him during these night wakings. He is still really keyed up by light, and sleeps best in a totally dark room.
The initial bedtime in the crib was hard, around 6-8 months. Sometimes I nursed him to sleep, most times I didn't, but nursed earlier in the evening. He had to be tired enough and sleepy eyed before we put him in the crib, or he would cry for hours, and get himself all keyed up. When he was tired enough and I had the timing of bedtime right, I would put him down, then swiftly walk out every time, and eventualy (few weeks) he'd only cry 10 minutes or so. The rule was if he cried more than ten minutes, we would go back in - either he wasn't tired enough (took him out and let him play longer), had a poo, had a toothache or fever (give tylenol), overtired (rock quietly in chair for a while) or something else was wrong.
Hated to hear him cry. Thought for sure there had to be another way to do it. Tried staying near his crib as he went to sleep - if he wasn't tired enough he thought it was play time, and would try and convince me to play with him. Super cute, but not the result I was going for. Around 13 months the paci went away - he developed a new cry in the backseat of the car that meant "Where's my paci? How dare you not give it to me immediately?", and my response was, if you're old enough to demand it specifically, you're old enough to do w/out it. A week or two without it, and the tantrums were gone and he was fine. Occasionally he sucks his fingers, but not all the time, just usually now when his teeth hurt or he's really upset about something I can't immediately fix.
After he stopped nursing at bedtime (14-16 months - I was too sore due to baby #2
to continue, or we might still be doing it), dad would put him down a lot, and rub his back. Somtimes that helped. When he was younger, the SLeep Sheep with its white noise sounds helped for a while, then not. The humidifier white noise helped for a while, then not. What eventually worked for us, and has for almost a year now (he's ~22 months) is, to help him stop crying at the initial bedtime we have the following routine: one of us parents reads him 3 books, makes sure he's sleepy, changed, etc., the turns out all the lights including the lights in the hallway that come in under the door, and lays/sits in the recliner and makes shushing noises. Everyone in the house is quiet for 30 minutes. Baby is placed in crib, whimpers/cries while mom does deep audible breathing in the recliner. After ten minutes fussing has stopped and he's usually asleep. I have to wait 10 minutes after he's quiet for his breathing to slow, and 10 more minutes for him to be fully asleep enough so that when I quietly exit the recliner (creaking noises) he doesn't wake at that or the opening of the door (it squeaks a bit). Often I fall asleep for an hour or so and then exit the room, and that works too. The key for us was, the crying while we are in the room is the "I'm mad at you because you put me down, but I'm mostly tired" cry, whereas when we left him in the room alone it was always the "you've abandoned me! and I'm all alone and so tired!" cry. The former was much easier to tolerate and he seems a lot less stressed over bedtime now. I do deep breathing really slowly in the recliner until he falls asleep, and that's enough to help him calm himself and fall asleep. We use a baby monitor in the mornings, and he knows we'll be in his room within 5 minutes whenever he wakes up, so now he has this "I'm waking up and you're not here yet, you better come soon or I'm going to get anxious" cry.
It took a while for him to trust we weren't going to leave him alone at bedtime, - when we first started staying in the room it took an hour after we put him down, b/c he'd cry for 30 minutes, but that cry period got shorter as he realized we were no longer going anywhere. I think the transition from 30 minutes crying to 10 took 2+ weeks. The crying period gets longer again if one of us is impatient several nights in a row and tries to leave before he is fully asleep and he wakes up. He remembers.
For naps, he nap on top of me in the recliner. He has to be tired enough, and I totally ignore him (of course don't, but I pretend to so I can be as boring as possible) as he cries with anger about the nap for 10+ minutes. He acts like he wants to crawl down, and I don't stop him. When he realizes I'll let him, he decides he doesn't want to leave mom after all (sometimes he makes it to the floor before this realization kicks in and then cries desperately until I pick him back up).
On really over-tired days he cries for 30+ minutes, and I am personally done hearing it. So I ask if he wants to sleep in the crib or on me. If he keeps crying, I put him in the crib for 5-10 minutes and lay back down in the recliner. When there is a quiet bit between crying, I ask if he wants to come and sleep on mom, and prompt him to say yes please. He does this, so back on my chest he goes. Usually he then grabs my hair (his comfort object), and then lays down and sleeps for 2-3 hours. I nap too. We've tried various times to transfer him to the crib, and it just isn't working yet. I've just accepted I'll get nothing done. Once baby #2
is here, dad may be the nap surface - we'll make all that up when we get there, but for now things are working well for us.
I should say, he spends 40 hrs a week in daycare, sleeps on a cot now with a blanket just fine for his teachers, and is generally a cheerful, well adjusted, happy child who enjoys going to daycare. Luckily we have a good daycare. It's only at home/with mom that naps/sleeping seem to be an issue.
Hope some of these ideas are helpful. Best of luck!