Hi there,
The four month mark can definitely be a tricky one. Around this time they really start to move from the newborn stage and into a stage of greater awareness of their surroundings.
Have you check out this post on Nicole's blog about the 4 month old schedule? Might be worth a look to get an idea of how your current schedule matches up with the recommend schedule.
Does he sleep in a crib or are you currently co-sleeping? If he sleeps in a crib, have you been able to try to nurse him just until he's sleepy and then put him down? Sometimes going through a few days of doing this, will help teach him to not rely on the nursing to fall asleep as well as to learn to fall asleep on his own. If you nurse him to sleepy, then set him down and he immediately wakes up, then try again…repeating as many times as you feel comfortable with. He may not get it the first day but after a few days of trying he might understand.
If you're co-sleeping, then you might consider that moving him to a bassinet by the bed or to a crib. Sometimes any movement by you or your partner can wake baby if he's in a light sleep cycle. There's also the possibility that he smells the milk during a light sleep cycle and this can wake him to want to eat. I really wanted to be able to co-sleep with my son, but it just didn't work for us.
I hope there's something here that you find helpful. Keep posting back and we'll keep working on getting you and baby to better sleep!