Persistent rash that goes away and comes back

So I've been getting this rash over my entire body since last summer, and it's getting extremely irritating. For example, there are some days in which I would wake up and find a horrible rash from the back of my head to my neck/body and limbs. But then there are also these days where I have no rash at all, and yet there are even days where my body/groin region is affected with these intensely itchy red regions/nodules that flake off skin and leave brown scabs when skin is scratched off.

I've been taking Benadryll to relieve the symptoms, but they always seem to come back one way or another. I went to my family doctor suspecting scabies, but the doctor said it was just dry skin. I remain skeptical because I also have this sort of crawling sensation throughout my body (parasite?) when the rash is active. My mom seems to have a minor version of this rash, and my brother/dad don't seem to be affected at all.

Any help?

P.S. I also recall that there was this kid I was babysitting last summer that had a very similar rash (brown scabs/red patches) - could he have transmitted a skin disease of some sort? And is there a possibility that dog fleas/other external parasites could cause this? Thanks again.