So, how many times a day is he nursing? Is he nursing through the night? What were/are his weights? You mention he is playful/ curious/ alert.... I assume this means he is meeting all develpmental milestones. Has he been sick at all?
This sounds a lot like my 4 month old. She's already teething and is either uncomfortable or has hands in mouth most of the day - she'll even put hand in mouth in the middle of nursing so we finish way earlier than I'd expect. She's also fascinated and curious all of the sudden - very distractible. But very happy and healthy (not sure of weight comparisons). Oh, and she's sleeping through the night. How many diapers you go through in a day is always a good indicator.
My first thought is teething. Is he drooling?
At this age, falling asleep may not be the same as it used to be. He may be refusing it because he's not hungry, but tired and needs a little more help falling asleep these days. If you aren't already, you might try swaddling, bouncing/jiggling, while making a shushing sound and have some white noise in the background, to help him fall asleep. ...and a pacifier if you want. (use a fan or something like simplynoise.com)
Look through a copy of Happiest Baby on the Block. It can be very helpful for this time.
Is there a reason you're weighing him frequently?
When you say "refusing to eat" do you mean that he's not eating at all, or just that he's being fussy at the breast sometimes?
Is he getting any bottles?
How do you feel your supply is doing?
Are you feeding on demand/offering the breast often? Right when he wakes up while he's still sleepy? What does your typical day look like in terms of breastfeeding and naps?
There are lots of possibilities, but with a little more info, we should be able to come up with something. Good thinking to come here and ask!
Something you could try in meantime: Right before you're going to feed him, pop a binky or finger in his mouth to get him calm and in a sucking mode, and the quickly switch it out for the breast.
My son is 4 months old and also teething. He is very uncomfortable and constantly trying to put anything in his mouth.
He will go on a nursing strike for a few days at a time. It's extremely frustrating, but I know that it's because he's in pain. I found the best way to get him to nurse is to pump an ounce or two and give it to him with a bottle. He then wants more and will nurse. He rarely ever gets a bottle. Other times when he gets fussy at the breast, I try to stroke his head and make a quiet "shhhhhhhhh" sound. It seems to calm him down enough to nurse. Another thing I do is give him some Tylenol an hour before I want him to nurse. It helps with the pain.
Try and stick with it. I know how frustrating it is and how tempting it is to just give up... but think of all the benefits you are giving your son. :) Good luck!!
He doesn't eat at all! As soon as I bring him down/close to me to nurse, he gets fussy, arches his back and pushes away the breast with his hands. I weigh him to see how he's growing. He lost a lot of weight first week of his birth and was in 16 percentile (Though his birth weight was good 7.4lbs). Ever since, I get his weight regularly, ESP now that he's not eating. I offer him the breast often, but he won't take and I don't force him. I have a good milk supply. I used to have a lot up until 10 days ago, before my period started.
I'm at a loss here, don't know what happened all of a sudden to make him not eat. I still think the vaccination played some role. I welcome any recommendation. Some times i can tell he is hungry, yet he wouldn't eat. He doesn't like the bottle either. My husband tries it 2-3 times a day. At best he takes about an ounce, or refuse it altogether as well.
Thanks for all your responses and comments.