Are Constant Fatigue And Discomfort In Stomach A Cause For Concern?

I recently returned from a week long work trip to Nicaragua. I've been back for one week and still feel constantly tired and have a funny feeling in my stomach even though I have consistently gotten a minimum of 8 hours of sleep, have been eating normally and have had normal bowel movements since my return. I have no other obvious symptoms of any standard illnesses. Any ideas of what may be wrong or if I should contact my doctor yet? Thanks