I had my period last month and everhting was fine a couple days after my period I had unprotected sex my boyfriend pulled out, which I know is not the best thing, but I am also on birth control. It is not a couple weeks later and every time I eat about 20 minutes later I get really bad cramps and have diorreah. I don't know why this is happening. I don't feel sick or anything else. Could I be pregnant? What should I do?

That doesn't sound like a pregnancy symptom to me. If you've had diarrhea for more than 3 days, you should see your doctor. It sounds more like you have a bug of some kind.