What Causes Bowel Movement After Eating Food And Sharp Stomach Pain?

i had food poisoning 2 months ago in november of 2010. Ever since than, my stomach has been going crazy over a lot of foods i eat and i'll usually have to use the bathroom shortly after i eat any meal. Recently I started getting a sharp pain in my stomach above my bellybutton in the center. It's like a needle-like pain but only happens for a split second- but the fact that it's happening is concerning..especially when my stomach has been hurting me for 2 mo. now. i went to the emergency room and had blood taken and a uranalisis done but both tests came up saying nothing was wrong with the tests. i have no idea what to do next. i've taken nexium tablets which didn't help, i've taken tums - they don't help, i had an ultrasound which said nothing was wrong. can you please help me?