stomach pains

Anyone else suffer from stomach pains after eating heavy foods? I'm barely gaining any wight cuz I'm barely eating cuz EVERY TIME I eat, no matter what it is, it makes my stomach hurt. I told my doctor & she didn't tell me what it could be. They told me today at my WIC appointment that I need to eat at least 6 small meals a day & that's so hard cuz everything upsets my stomach.