Seems like my baby is Sensitive to ALL formulas? Anyone have this issue?

First and foremost, I don't want to be criticized about not feeding, etc. I AM feeding my baby milk (pumping) right now and have been. He is about to turn 6 months. I am drying up because my schedule does not allow for me to pump as often as I should. Work ALL day then school ALL night M-F. I have an intense schedule and I'm lucky I've been able to offer my baby milk this long. Sometimes I am not able to keep up with my baby's demands and have to supplement with formula. Ever since he was born though, there has always been something weird about him being sensitive to everything. I even have to watch what I eat. I still don't know if he has a milk allergy. All I know is that he gets bad stomach pains and gas every now and then from something I probably ate or the formula if we ever give it to him. I have tried all the similac and enfamil brands and the HYPOALLERGENIC stuff. How in the world is my baby still sensitive to hypoallergenic formulas? Anyone have this issue where your baby is just sensitive to everything? Do you know what it could be? Could there be something else in the formulas that the baby is sensitive to?