It sounds like eczema, which would require a topical cortisone cream to get better. Fungus is possible too, but less likely. I suggest you get an over-the-counter antifungal cream (clotrimazole, Lamisil) and try that twice a day for 2 weeks. If that fails, you'll need to see a doctor in person. I don't see any connection with the other medical problems and medications you mention.
Best.
Dr. Rockoff