Does anyone recognize this rash?

Sa

I’ve had this really mild rash on my abdomen for several months now. It started when I developed mono. I showed it to my doctor when I was diagnosed with Mono and he was not concerned about it at all. But it still hasn’t gone away 🤷‍♀️

Any ideas?

Not itchy or painful, it’s slowly moving further up my abdomen towards my chest, becomes darker when I’m warm like when I get out of the shower.