Since you are breastfeeding, I would highly suggest NOT going to a 4 hour schedule right now. Even at 4 months, many breastfed babies are not ready for 4 hours, and it can really lower your supply.
I think it sounds like one of two things. It could be developmental...has your baby started rolling over or is your baby getting ready to roll over? If so, it might be due to this. If it is, I'd suggest perfecting your swaddle so that it's really tight and maybe your baby won't be able to get out of it.
The other option is paci addiction. Right now you're just waking up a few times to put the paci back in, but watch out because it could become 20 times a nite before you know it. you might want to check out the props board for some more info.