You cannot become pregnant when you have pants on.
You cannot become pregnant when you have pants or other kinds of clothing on that covers your genitals.
No, seriously, listen up:
No, not even JUST you but no one else, because you think you are some kind of one-in-a-million-something-or-other: Nobody is that special, not even you. (Which is not to say you are not special: I am sure you are. Just not THAT special.)
Not even unicorns. Or magicians. Or flying pigs. Nobody.
There IS no one-in-a-million-with this. Only a none.
Last time: Were you wearing pants during anything you are worried may have caused pregnancy?
YOU DO NOT NEED TO BECAUSE THAT CANNOT HAPPEN WHEN YOU ARE WEARING PANTS.
IT JUST CAN'T.
(To find out how pregnancy does happen,for real, and all that is required -- including an utter lack of pants -- have a read here.)