What Causes Low Grade Fever Along With Stomach Pain?

Ran a low grade fever 100.9 for three days fever is now been gone for 2 day I feel better but I am still have gas pain and stomach is tinder. Have very small stools with mucus in it. Thinks I had some bad fish. What should it take to help? Pepto or antibiotic Let me try this once before I commits to see if this is legit