Suggest Treatment For Dark Spots On The Stomach

I found black/dark spots on my stomach and my side and now it has spread to my back. I first noticed when I got out the shower and I was itching. They don't itch anymore but they're very visible. The ones on my back itch but not that much. I wanted to know what it could be. I was diagnosed with a rare kidney disease and with the medication, my immune system got worst. I work at a fast food place and I take showers when I get off usually.