Why does my stomach hurt or feel painful after i eat? i haddiarrhea/dehydration a couple of days ago.

Several possibilites: This could be due to a few different reasons. It could be heartburn or gastritis. It could also be a bad gallbladder. Another possibility would be irritable bowel disease. If it is a recent concern, it also could just be from a viral infection. If your symptoms continue or worsen, you should see your doctor.

Depends, see your MD: This kind of specific problem really needs an evaluation from your doctor as problems can range from minor like a viral gastroenteritis to more serious things. Talk to your doctor.

Stomach pain: Some times after a stomach infection you could have some inflammation to the lining. This would show up as pain especially after eating since that is when your stomach releases more acid. Could try some Prilosec or Prevacid (lansoprazole) otc to see if it helps. Should get it checked if not better in a few days.