Could I be pregnant?

So this is really weird but I am going too ask it anyway. I have never had sex and do not plan on doing it for a while however I was giving my boyfriend a blowjob and did not want him to cum in my mouth so he said why don’t I cum on your ass and I agreed. Well he cam a lot and some of it started to drip and I told him to get a paper towel and then wiped it up but I’m not sure if anything dripped in my vagina. I was so worried that I got him worried and the next day we got plan B. I am late on my period by 8 days but I have read that plan B could make your period late. I took a test and I was negative. I feel like I’m paranoid lol but can someone ease my nerves. Most of the people I talked about it said it was a very very very slim chance.