Weird pains..?

I have been having these strange stomach pains for a few months...The pain is from my belly on up, and I usually have it everyday, the amount of time that it last varies, as does the intensity. I thought it may be caused by stress from school, but now I am home for the summer and very relaxed and the pain is still happening. I have taken Pepto and Mylanta as well as other pain relievers, with no success. What could it be??