To me, it sounds like you might have a food
IBS is Irritable Bowel Syndrome. Basically, your nervous system likes to freak out your GI tract when you eat certain foods. The food trigers are different for everyone, so you might want to experiment and see what you do and don't get sick from. Symptoms include cramping, bloating, diarrhea, constipation, nasuea, and sometimes vomitting.
Track your symptoms for a few days with a journal.