help please ladies ‼️😘

OK... so I'm the typical 18 year old teenager who has hardly any knowledge about sex. I've been with my boyfriend for 2 years and we always used the pull out method. Tonight, I was feeling frisky and I'm on my last day of my period (still a little blood) we were having sex and then my step dad came in my room while I was on top and my boyfriend cummed in me while he was talking to me. So my question really is... what are the chances of me getting pregnant and should I wait to take a test or anything? I was going to get the morning after pill but not clue where or how much! I live in the UK! He's never cummed in me before! Please help me ladies, much appreciated xxxxxx