Dear friend, You rash can be for various reasons which you may need to identify... 1. Most coomonly it should be a fungal infection (Candida) if you has an unprotected contact. In such a case it would look like red-white , raised dots and would create a bad odour. 2. It can be other STD also but those dont usully present with a Rash, 3. So you should try to treat yourself for the Yeast infection first with applying a clotrimoxazole gel (like candid). It will show improvement with in two-three days if it is fungal one. 4.If it doesnt you need to visit a physician/dermatologist as it is best diagnosed with a visual examination by a doctor. 5. Stay away from unprotected sexual behaviour in future! Take care!