It's called splash pregnancy. It's very very rare though. I highly doubt you are pregnant. That happened to me once, and it was a total false alarm. Don't worry too much, you should be ok.

I thought that sperm wasn't strong enough to make it through fabrics.

I don't think so. I've had a few scares this way. Let me know what happens! I agree with the whole thinking that sperm couldn't travel through clothing. Especially more then one layer and the thicker the better. Corrct me though if i'm wrong.

^^ this is happening to me.. But 2 weeks later I got my period dead on date.. But I have the feeling of anxiousness... However I think this is due too just starting my first ever pill which is the progesterone only anyway. Now me and my bf are very careful.. Wash our hands throughly after he ejaculates and we take it in turns... So I can wear jeans or something.. In case! Xxx