My 3 year old has been sick for over a week!?

I took him into the doctor one week when he was complaining of his throat hurting.. He had bumps on his throat and he was complaining of his belly hurting. They said it was strep.. did not run a test just said it was strep. He was on antibiotics for 10 days. After being off for two days he throat was bothering his really bad again, and his stomach. I took him into the doctor again. He was dehydrated and put into the hospital. He was there for 24 hours. They did a CT scan of his abdomen to rule out appendicitis. He also had a test for ROTAVIRUS MONO and STREP. All negative! He was on an IV for 24 hours for dehydration and they let him go. He is now home and still says his stomach hurts and crys. He also is saying his throat hurts and had a VERY bad cough and congestion. His fever goes from 99 to 102. I JUST WANNA NKOW WHATS WRONG WITH MY KID! Anyone have anything like this happen before? Or any ideas? He goes in for his check up this Fri to see how he is..