Hi there ~
I understand your concerns. I believe that the rough itchy skin rash
around your waist is a fungal skin infection
. However if you have had unprotected sex in the past and have the suspicion of probably having a sexually transmitted disease
including HIV I advise you to consult a doctor for the same. An STD profile and a urinalysis
will reveal the problem on hand and a doctor with suggest an appropriate solution. I hope this helps.
Take care and have a lovely day!