Hi,
Yesterday I met a random bar girl. She had her legging on (a type of skin-tight garment that covers the leg up to just below the stomach). I had my thin-cotton underwear. I was laying on bed and she sat on my penis and danced for 5 minutes until I ejaculated. Since there are 2 thin layers (Her legging, and My underwear), I am not sure if something passed through those.
Note that I didn't see her genital area, and she didn't see mine. I only touched her stomach. What are my risks for STDs from this encounter?