I feel nauseous every time after i eat and occasionally will have loose stool or diarrhea about 15 minutes after. what could this be?

Be seen: It sounds like irritable bowel syndrome, but you need to see your physician or gastroenterologist.

Gallbladder: Those symptoms are suspicious for gallbladder disease. An ultrasound can safely and easily evaluate your gallbladder and bile ducts, and a blood test of your liver enzymes would be helpful. Other possibilities include gastric ulcer, inflammatory bowel disease, irritable bowel disease. See your primary care doctor.

Abdominal symptoms: Could be stomach or duodenal ulcer or gastritis, gallbladder or pancreas issues. You need to have a physical exam by a doc to get the work up started.