Can i get pregnant through dry humping? i wore panties & sweatpants, & he was wearing boxers. but my sweatpants had a white ejaculation stain on them.

Extremely low...: It's very unlikely because sperms will die soon out of their "native" environment of semen. But exactly how long is unclear. Like we see that a person dies within minutes after stopping breath; so & similarly, we may assume sperms will die within 10-30 minutes. In your scenario, all-in-all, the likelihood to get pregnancy is almost next to zero.