Help!???

I know no one here is a certified doctor but I still want to know if anyone might now what this is. I got it Wednesday around the lower part of my flabby tummy. Today I have it from my stomach to the side of my hip and between my inner thighs( all the parts in the picture) It doesn’t hurt but it does itch. To be clear, I have been on my period for the past week and a half so it’s not something sexually related. (My husband thinks it might be a heat rash) Should I go to the ER? Will it clear out on its own ? Or should I get checked out ?