Could my girlfriend be pregnant by dryhumping?

Hi,
Welcome to ehealthforum,
Pregnancy does not result if semen or pre-cum has not come in contact with vagina. There are no studies to prove that sperms can swim through fabrics (unless it is thin and lightly woven and there is presence of ample vaginal wetness). Wait and watch for her periods. Look out for development of any new symptoms if pregnancy is suspected. She should visit her gynecologist for further evaluation and assistance if she does not get her 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 her started on suitable regular birth control measures to be protected (after her periods). She should be regular with birth control use as instructed. Avoid having unprotected sexual contact if you are not ready for pregnancy.
Take care.