I definately think you should look into getting another pediatrician. If the one she's seeing right now isn't concerned, especially with you being so worried about it, he's not doing his job. I would think a good doctor would refer you to a dermatologist and definately a child physcologist. This could certainly have to do with Dad walking out and not being in the picture, a new Dad and a new sister to share the attention with. Good doctors will be able to get to the root of the problem. Good luck!