Contact dermatitis from chafing seems indeed to be the most likely diagnosis. Fungal infection does not seem possible, nor STD's. I am really not sure why you seem to not be getting better. I can only speculate that either you are doing something to irritate the skin (rubbing, repeated checking of the skin), or else that you are over-interpreting mild redness and chafing that are meaningless and best ignored. There is certainly nothing to worry about here, and no reason whatsoever for you to avoid working out. By the way, creams do not and cannot destroy a layer of the skin--desonide in particular is safe to use in the groin indefinitely. I advise you to check in with the dermatologist again. This rash is having a far greater impact on your life than it ought to.
Best.
Dr. Rockoff
Thanks for your answer. Perhaps I am over-interpreting the redness - I have quite pale skin I guess that makes it seem like more of a problem. Do you know of anything that might reduce the chafing when i workout other than applying baby powder to the area?
I forgot to mention that I have not been sexually active for quite some time - I can rule out any chance of an STD