You cant really know and it really doesnt matter, virginity is just a social construct and whether he did or didnt accidently push it inside your vagina doesnt matter, you wont change or anything. Maybe you can ask him? If not no big deal do it when youre ready you decide when you lose your virginity, even if you did have sex. I will mention it isnt good to go from anal to vaginal sex for hygiene purposes, and that's what the discharge might be, Id go make sure you didnt get anything from that. If you do in the future just wear a condom after anal.