Can you get pregnant if your boyfreind comes outside your thin sweatpants?

I was giving my boyfreind a and he came outside my sweatpants on the crotch region. I was wearing a thong but it may have been a little out of place and the sweatpants were pretty thin materail..could i be pregnant? could of the sperm got through my sweat pants? plus even if i did could it really swim all that way to my egg? PLEASE help