My 4 year old is complaining about his tummy, his temperature is 38.5 degrees. what do i do, what can i get over the counter for him?

Depends on details: For minor illnesses like a cold, fever and aches go away by themselves. Most people use over-the-counter drugs like Tylenol (acetaminophen) for relief of such symptoms. For example, if a strep throat bacterial infection, antibiotics are given. If viral stomach flu, antibiotics aren't needed. A doctor can evaluate to give a diagnosis, especially if a person has more than minor, temporary fever.