It sounds like possible psoriasis. Psoriasis affects the roin in the places you list, and looks like red, dry skin. Psoriasis in the groin is not contagious and very easy to control. I suggest you make a dermatology appointment. Meantime, try over-the-counter 1% hydrocortisone twice daily and moisturize on top of it as needed. You should do fine, soon.
Best.
Dr. Rockoff
Dr. Rockoff