My dog has a rash of some sort, please help!?!?

I know it is most likely ring worm but it is accompanied by these medium sized bumps on his underbelly. There are the circular abrasions(which I am almost certain it is ring worm) and then the bumps. Are the bumps ring worm also or is it something else? Also, what can I do to treat it? I have put Tea tree oil on it recently but are there other things to put on it?