This is not a reply to make you want to do that more often..
But me and my gf used to do that all the time and she never got pregnant..
Though alot of things with her body started to change and stuff..
But.. no pregnancy.. But.. It's not a good idea.. and the stress level thats caused because of it sucks..
So.. when you get in the mood next time and ur about to stick it in.. just remember.. its not worth it.. run away .. lol