What is this armpit rash?

I’ve had an armpit rash for so many months and I can’t figure out what it is. It doesn’t itch and it’s not painful but it’s always there - even if I don’t shave. It looks more red after I shower so this isn’t it at it’s worst.

I’m going to the doctor soon but I’m wondering if anyone has any guesses as to what it is? I’m thinking maybe just eczema but no moisturiser or hydrocortisone cream has made it go away..