I Have Been Experiencing Nausea, Vomiting, And Diarrhea After Meals.

I have been experiencing nausea, vomiting, and diarrhea after meals. Often, I have no appetite and force food in order to take medications. In addition, I seem to have a metal taste in my month regularly. I would like to know what could possibly be causing this. My diet has not change much (existing of vegetables, fruit, etc.).