A.,
It sounds like he has a food intolerance issue to something you are eating. My son was majorly fussy to the point where I went on an elimination diet and figured out he's intolerant to dairy and allergic to soy. If I would have switched him to regular formula he would have been a very sick little boy. Check out this info http://www.kellymom.com/babyconcerns/food-sensitivity.html Something like 75% of babies who are "colicy" are actually intolerant to dairy proteins and since most formulas are based on cow's milk, they will make the problem worse, not better. And since most babies who are sensitive to cow's milk proteins are also sensitive to soy, you are likely to need to go to the hypoallergenic formulas which can be really expensive (the ones it the grocery store are "less" allergenic but if those don't work, there is an even "less" allergenic formula called Neocate that is special order and $45 a can. Yikes!
I started the elmination diet in December and I started out eliminating dairy, soy, eggs, chocolate, caffeine, nuts, tomatoes and citrus. At this point I'm only eliminating dairy and soy but I still eat the other things cautiously. My son is healthy, happy and virtually fuss-free. I'm not saying being dairy and soy free is easy but it is worth it. Oh, and to do it successfully, you have to eliminate hidden dairy and soy so you have to read labels. Dairy is fairly easy to avoid but soy is much harder because it is in so many foods. I've basically just eliminated most processed and prepackaged foods from my diet. As a bonus, I lost 20 pounds just by eliminating dairy and soy.
T.