Rash on 3 year old

My 3 yr. old son started with a skin blemish on the side of his thigh. I didnt think anything of it, and thought it just looked worse than it was because he scratched it raw. I would put neosporin on it to help it heal. It started getting a little better, then I started noticing a rash on his belly and back. The rash looks like little pink/red bumps all over, they are all spread around, not just cluttered in one spot. Then I thought maybe his soap and the cold weather may have been irratating him, since he does get dry skin in the winter time. Last Wed. his school called me because the rash was now on his hands on the sides by his pinky, around thumb and a little between his fingers. I took him to the doctor right away and she said she just thought it was dermatitus. She gave us medicated lotion to apply 2 times a day, and we have switched to a gentle, mild, sensitive skin soap. His belly and back are looking better, but now it is all over his legs! Then tonight I was giving him a bath and I am starting to see it on his face, cheeks and tips of his ears. I just dont think it is dermatitus. There must be something causing this! He dosent have anything on his feet, genatils or armpits. Right now his legs are the worst and on his cheeks. He still has bumps on his belly and back, but they are no longer red. They do itch him, but not horribly. It has been about a month since he got the spot on his thigh and going on 2 weeks for the bumps all over. Please help, and advise would be great. I am waiting to get him in to the doctor again, but in the meantime it is driving me nuts. Thank you!