Hi Amy,
I'm so sorry to hear your little guy is having such troubles! Is he gaining weight alright?
Anyway, it could very likely be reflux, that was my first thought. But I wanted to let you know that sometimes an allergy of some kind (cow's milk is usually the main offender in lo's as far as allergies go) can cause reflux. Do you eat a lot of dairy? You can try cutting back or cutting it out all together for a week or so, and see if his condition continues. And although it generally takes a few weeks to leave the baby completely, you should see at least some improvement if this is the problem... Does it seem to be worse when he's drinking more formula, or is it the same whether your just breast feeding, or bottle feeding?
I hope he starts to feel better soon!
Whiskers