Need help identifying and treating a persistent rash

This rash has been on my neck shoulder, tummy and back for a while now. It flares between showers or with heat, it seldom itches. Dont believe its something in my diet. is it some kind of exzema or dermatitis? a fungus? Could someone please tell me what it is and how to treat it? would Cortizone help or do i need prescribed medicine? Summer is coming and um afraid of people seeing it and judging me for it.

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