Hello,
It can be due to chafing or friction rub or simple dermatitis skin.
Chafing is a continuous rubbing of the skin that causes redness or soreness. It occurs when the skin becomes irritated by the friction caused by rubbing – either against other skin or against a foreign material.
Wash the area with fresh water. Do not use any cosmetic products at the sites. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments. Maintain hygiene and try to keep the area clean and dry, wear loose-fitting cotton clothing. Also use mild soap like dove. Avoid deodorant / cosmetics.
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 doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
If u need more pic I can upload them more clearly I do notmhave any rash on my body plus I masterbate 6 dayss ago after sex with lube u think it allergy or yeas0t infec