Hi,
Welcome to ehealthforum,
Sperms cannot pass through fabrics, but can stay alive for about 20 minutes even in dry condition. If pre-cum or semen has come in contact with vagina during sexual contact, chances of pregnancy are possible (chances are high if you were during your fertile days at the time of sexual contact). Wait and watch for your periods. Look out for development of any new symptoms if pregnancy is suspected. Visit your doctor/gynecologist for further evaluation and assistance if you do not get your periods within 10 days of expected period dates, or gets abnormal bleeding. If pregnancy gets ruled out and if you are not ready for pregnancy, but intend to remain sexually active, you should consider getting started on suitable regular birth control measures to be protected (after periods). Be regular with birth control use as instructed. Avoid having unprotected sexual contact if you are not ready for pregnancy.
Take care.