After I eat I always seem to get diarea wht can cause this?

Maybe lots of things. Anything from inflammatory bowel disease (crohn's and ulcerative colitis), celiac sprue, tumors, partial bowel obstructions, parasites, infection, and irritable bowel syndrome, among others. See your doc.
Many things. Many things can cause diarrhea after eating. The list of possibilities include anything from an infection, to an inability of your intestines to absorb liquid or fat, to something called inflammatory bowel disease and so on. You need to have a detailed talk with a md to fire it out.