May be a fungal infection of some kind. You're gonna have to go see the doc. You could always try an antifungal cream of some kind but why mess with it. Schedule an appointment with a dermatologist. They should pretty much know. It doesn't appear to be an STD but I certainly am not an expert.
Hello,
It can be due to fungal infection, eczema, psoriasis skin or lichen sclerosus. Lichen sclerosus is a chronic disease which effects usually the genital areas in postmenopausal women. The exact cause is not known and can be too active immune system and hormone problems. Some people have also proposed a genetic and hereditary
basis of disease. Treatment consists of strong cortisone cream or ointment on the skin. Other treatment options include Retinoids, vitamin A-like drugs, Tacrolimus ointment and Ultraviolet light treatment.
I would suggest a clinical examination done by a dermatologist. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.