Hello, I Am A 44 YO Male And Have Developed

Hello, I am a 44 YO male and have developed a rash around my anus that I have had for about three months. I have seen my Primary care doctor and he recommended I see a dermatologist. Saw the dermatologist and he recommended a anti fungal creme which I used as directed with no clearing of the rash. Also saw a colorectal surgeon as well who took a biopsy of the affected site and it came back negative for bacterial and staff. Colorectal surgeon referred me to a Rhuematologist for a possible auto immune issue causing the rash. Also started Diabetes meds within last 4-5 months ago and I thought I may be having a reaction to the meds. Any help would be greatly appreciated as the rash is weeping and making life miserable.