Hi, I was diagnosed with a stomach flu a month ago, but since then I have a significant loss of appetite, i have nausea, and headaches. My poop went from being twice a day to an oily substance, now i am completely straining. I went 5 times yesterday, but my stomach hurts in addition to my back and legs. I have been eating healthy, whole grain, fiber, vegetables and even drinking water. What could be the cause for this and what should i do?