Farrah Abraham -- Worried She Could Get Pregnant THAT Way

Newly minted porn star Farrah Abraham is so worried James Deen knocked her up while filming their infamous sex tape ... she peed on a stick.

Sources close to Farrah tell TMZ ... the former "Teen Mom" star hadn't had sex in more than a year before James got her ... and the duo didn't wear condoms while filming ... and Farrah wasn't on birth control. Basically all the makings for an after school special.

We're told Farrah recently missed her period and started freaking out, thinking she was growing a little porn spawn. So she went shopping for a pregnancy test at her local pharmacy.

We're going to go to out on a limb that she's NOT pregnant ... for 2 reasons.

1. We've seen the tape, and you don't get pregnant THAT way.