Can precum penetrate through underwear and then through jeans ? and if it does so,will it be motile enough to fertilise and egg?

No, pregnancy is not possible in above circumstances, fabric acts as mechanical protection. Contraception remains otherwise key in avoiding undesired pregnancy and associated anxiety and when intercourse is likely to occur.

Precum has no sperms. Even on a remote possibility if it does -it has to enter inside the vagina to cause pregnancy- which in this scenario it did not

While you are not at risk of pregnancy from this episode, your behavior is putting you at risk of pregnancy and STDS. Visit this site for guidance on safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines Get HPV vaccine Use contraceptive all the time, every time. Wish you good health!