Persistent Rash Below Belly Button, Worsens With Sweat, Leaves A Permanent Scar. Cause And Cure?

I have a rash just below my belly button that has been persistent for a few years now. I once saw a dermatologist and they told me it was due to the nickel of my jeans, but I don t think that is the case, specifically because it becomes irritated even when I m just wearing sweatpants. I ve noticed that it gets bad when I sweat sometimes and when I wear underwear that does not have a 100% cotton waistband. I am thinking perhaps it is the detergent that I use, or my coming into contact with certain materials. I m just hoping to find out if any sort of cream will work, since the original steroid cream my dermatologist gave me years ago seemed to just lessen the impact of temporary rashes (but did nothing to really help my skin return to it s full original form). I am frustrated because the rash is leaving an almost permanent part of my skin with a reddish/darker area that is noticeable if I take off my shirt.