red blotches on belly and arms

[codalove]

My pup, coda, went to the vet for his rabies shot about a month ago. Back then he had a small rash that, honestly, looked like it came from his bed. We replaced his bed with a new one in hopes that the rash would stop. It stopped for a month. The vet didn't mention anything about his rash while we were there.
Recently, a couple days ago I gave him a bath with whiff shampoo and these rashes got SO much worse. I'm taking him to the vet on Monday but I'm still concerned. He's not tired, he doesn't itch them, but he's losing an unusual amount of hair. I am extremely concerned and am wondering if someone has come accross this and if there's anything I can do to make him feel a little more comfortable until I can take him to the vet, because I'm sure these hurt him.
Here aare what I'm seeing invade anyone has experience with it:
Big, red, open sores and hair loss.
They scab up fairly quick, then go away, but always manage to come back.