Answers Please!!!!

So tonight my boyfriend and I had anal sex; not the first time so it was nothing new for me. I have SEVERE anxiety around the thought of being pregnant and he is very supportive of it, it's just always nice to here from GIRLS and their advice along with his.:) 
So we were going and it felt halfway decent and he asked if he could ejaculate in my anus, in the moment I was fine with it but now I'm here at home freaking out and needing answers!! He ejaculated in me and then before he pulled out he put his hand underneath to catch anything that dripped out. He then grabbed a towel and cleaned me up. Not that my boyfriend isn't trutworthy, but WHAT IF some ejaculation dripped down into my vagina? What are the chances of pregnancy? Should I be worried?!?! Today is the day AFTER my fertile window and my actual Ovulation Day was 2 days ago.