My son has had a month long fever and unexplained body aches. Has anyone ever experienced this with a toddler?

My son is 2 years old. His fever has ranged from 102-104 for a little over a month. We have taken him to 4 different emergency room doctors and his pediatrician three times. They all keep telling us that he seems to have a virus, but they all agree that a month is a little long to have a virus. We've had xrays done, blood drawn, urine taken... and they can't find anything. "It must be a virus" is what we always hear. So, what I'm wondering is if anyone else on here has had a child with similar symptoms. It all started at he beginning of May, with a fever... then a few days later we noticed the body aches. He seemed to favor different body parts at different times... sometimes when we tried to pick him up, it would seem like he was favoring his arms and shoulder. Today, over a month later, he's wobbly and uncomfortable when he walks. Making it seem like he has pain in his hips or thighs. For a few days last month, he also grabbed at his penis. Making me think he had a urinary tract infection. But all tests came back negative for that. Other than these symptoms, he is shaky and whiny... crying almost all the time. Sometimes, the symptoms will almost disappear entirely, and we have a happy, normal 2 year old. But the symptoms always come back. I meed some real advice here people. I don't want to hear that I need to take him to the doctor because I have obviously tried that. I just want my baby to feel better. Please help.