I been having diarriah for the past 4 days feeling nausiated loss of appiteite and when i bend down or stand up from a sit severe pressure on my head?

Sounds like: Symptom of dehydration. If you cannot keep anything down and diarrhea persists, you will need intravenous fluids. If you can keep anything down, try rehydrating with gatorade. If you develop abdominal pain, especially in right lower quadrant, it could be appendicitis, so go to emergency room. If your diarrhea has any blood in it, this is also a bad sign.