Semen got on my gf yoga pants on the outside right were here vj is could it travel through and cause a pregnancy?

No. Yes.: NO... because in real life, clothing prevents pregnancy by preventing the passage of sperm, of penises, and of fingers. If not wanting to start a family, one can just keep his or her clothing on. It works quite well. That said, the answer to the question of "could something happen" is generally YES, because even rare things are possible (even if nearly impossible) in this world.