Jt'smum, I have nearly the same gap as you: dd is 4 mths and ds is 7. I'm afraid I don't have all the answers, but I'm working really hard to try and create opportunities for connection with ds these days. What I'm finding is that we have to work our schedule around dd a lot right now, as her schedule is always changing, but that it is possible to work in at least a little bit of one-on-one each day using a combination of her nap times and happy times. Lately, for instance, all three of us have been reading together for nearly an hour every night (I usually nurse dd on and off while reading), and then I've been leaving her with a toy in my room and tucking ds in in his room for about ten minutes. Ds and I do "highs and lows" together at this time, and I cuddle ds, and he really values the 'without baby sister' time even though it's brief.
Now that dd is big enough to go on my back, I think we'll be able to do even more mommy-ds time. The other day, he and I played tennis while dd slept in the Ergo, and we both had a blast. Last night, I went out with dd in the sling and both she and I watched ds play some basketball, and she giggled like crazy each time he raised his arms to shoot. Now he's all proud that he got his first giggles out of her.
I try really hard to stay away from language that blames dd for my behaviour. For example, if ds wants to play and I can't because I have to nurse dd, I don't say that, I just say, "I'd love to in about half an hour". And then I make sure I follow through. I've also been really careful not to expect ds to feel a certain way or act a certain way in regards to his sister. So, for instance, ds has decided that he can't handle spit up and wants to avoid touching anything to do with it, including his sister. I'm respecting that because he's using it to express his feelings around having to adjust to everything. So, dd doesn't go on his bed and her stuff doesn't touch his chair in the dining room. Also, if I ask him for help to do with her and he refuses, I let it go (and when he does choose to help, I make sure he knows it's much appreciated). I'm thinking by letting him have those boundaries, and listening with empathy when he expresses negative emotions about her, he'll get the message that she isn't as much of a threat to him as he might fear, kwim?
As far as the bed-sharing goes, I started preparing ds for not being able to do that when I first became pregnant, and we had several final 'sleepover' nights leading up to her due date. I knew I would be too worried about safety and I wouldn't get any sleep if both kids were in bed with me, since ds is a VERY active sleeper. But when he was really wanting proximity, I did let him sleep on the floor beside us on a single mattress, which he thought was fun. And he comes in for morning cuddles when he feels like it. Maybe your dd would enjoy having a mattress near your bed?
Finally, one of the things that seems to really help when ds is feeling shafted is for me to reminisce about when he was dd's age, and talk all about how much I cuddled him, sang to him, bounced him, changed his diapers, etc. He likes to hear about when he was little, and it also gives him the message that all
babies require and receive a lot of care, not just his dd. He had his time, too.
I'm reading a good library book right now called "Sibling Rivalry, Sibling Love" to help me get things off to as good a start as possible. Maybe your public library also has it.
Hugs to you, mama. The whole sibling thing is hard even for mamas with