Hi, I'd really appreciate it if someone could help me out.
Well, basically what happened was that my boyfriend and i were trying something that's new to both of us. we were engaged in dry sex, fully clothed, and then we undressed and he slid his penis into my backside, not into any holes though. There was no orgasm, but I'm not entirely sure if precum was present, and if so, how much.
The thing is, my underwear was partly pulled down. There were no wet spots on the back of my underwear (or nearer the front) that could have been caused by precum.
My questions are these:
1. Is it possible for precum to come into contact with fabric and not stain it? Or is it possible that the precum slid directly to my vaginal opening? We were standing up, if it helps, so gravity would probably not have taken the precum to my vulva.

2. How much of a pregnancy risk does this pose?

3. Once precum reaches the vaginal opening, do the sperm immediately swim up or does gravity play a role? In other words, does the precum have to be pushed up into the vagina in order to pose a viable pregnancy risk?

My last period was around the 10th of August.

Any advice or help is very much appreciated, thank you for your time