"I have this rash that has not gone away for the last month."
Tinea Cruris is also known as jock itch and is a fungal infection which is located along the inner thighs and sometimes the scrotum. As with any rash you should have this checked out and go on the appropriate medication. Resolution can take up to 3 weeks. Jock itch appears in moist skin areas and is not sexually transmitted. It is also not usually the result of poor hygiene.

"I got jock itch, does this mean I have to get tested for STDs?"
No. This is a common diagnosis and no other illnesses are usually suspected.