On a serious note and in an attempt to sound like less of an asshole. Pulling out is considered by many to be " better than nothing" with a 22% failure rate. So there's a 22% chance you can knock someone up. (I'm not comfortable with those odds.) As opposed to nothing at all which I think is like 60% or something like that. However, if pulling out gives you a false sense of security then you're liable to do it more often thus increasing your chances. And again, we all know that being on test reduces the likelihood of conception but ask anybody that's been around this game for very long and we all know plenty of guys that middled named their kid cypionate. Not really but that would be funny. So is it possible you knocked up your girl...yep. is it equally possible that's she's some trifling tramp that's been stepping out with your buddy Gary... yep. Good luck!