Can sperm travel through clothing?

My boyfriend and I were fooling around the other day and I've been kind of worried since then. We both had only underwear on and we were dry humping. He didn't ejaculate but I am sure there was quite a bit of pre-cum. I just want to know that if he DID ejaculate or if there was any sperm in the pre-cum if it's possible for sperm to travel through the underwear, into my vagina, and ultimately lead to a pregnancy. I'm 17 and I've done quite a bit of research and as far as I can tell the chances of me getting pregnant are slim to none but I want to be 100% sure. I want to make sure my boyfriend and I are being safe and responsible, so replies would be much appreciated!