Getting rid of boob rash

So I have this rash looking area between my boobs. It sorta wraps around my right side. I've been told its probably just sweat rash and to apply ointments to it until it goes away, but it hasn't. It kind of fades and then flares up again. I've seen others post similar problems on here before and have been told its some sort of yeast infection.

So I guess my question is if anyone can tell me whats causing this and what I can do to make it go away.

It gets itchy and feels and looks dry

Thanks