My son has a stomach bug i think as he has fever, cramps and vomiting. how can i relieve his symptoms. is it self treatable or does he need antibiotics?

Bug is virus=no abx: There are several dozen stomach viruses that trigger this pattern and none benefit from any antibiotic. Treatment is supportive. The main effort is to preserve hydration until they self heal. Small frequent volumes of fluids, apple sauce, popsicles, ice chips, etc all help. As the kid improves the volumes can increase/feeding start. As long as he can pee at least every 8h he is hydrated.