What IS THIS rash!?!

It started about 4 years ago, it only popped up after a hot shower, so I just thought it was the hot water doing it. But after having my child a year ago, it’s pretty much there all the time now, constant. And now it seems to have spread. It use to jist be in between my Breast, but now it’s under and actually on top on them.

I’m a clean person, and I shower almost every day.. so I have no idea what this Is. someone please shine some light onto this pleaseeeeeee