What Causes Rashes On Body And Pain In Legs?

Hi, my 5 1/2 yr old son has been complaining for the last 2 months that his rt leg hurts. He d wake up in the middle of the night crying. Thought it might just be growing pains . But last few weeks it has gotten progressively worse. I have to give him ibupropron 2-3 times/day. Tylenol just doesn t work. His pediatrician did x-ray and blood work, nothing looked abnormal. Then, 2 1/2 wks ago, he got this bad rash all over his legs and eventually on his elbows. Almost looked like blisters, big & puffy. Took him to dermatologist, thought it might be a viral infection. This rash is almost cleared up with steroids (both oral & cream). Then took him in to a pediatric orthopedic who also did x-rays, still nothing showed up. He does have an appt for a bone scan next week. But, now he has developed another rash all over his body. This rash looks different than the one before, little, tiny pumps (what I normally see rashes look like, compared to the other rash he had). Now today, he has been complaining his stomach hurts. He s not running a fever, just doesn t feel good. The pediatric orthopedic thought possibly these 2 symptoms were related (he doesn t know he now has another rash or stomach ache). Should I be overly concerned right now? Or is o.k. to wait till his appt next week?