I know it might sound stupid but I'm really worried right now.

I'm still a virgin / by means that I still haven't had penetrative vaginal sex. I've done other stuff though. Last week me and my bf had some time alone together and we got caught in the moment. All we did was foreplay/fingering/oral and little rubbing and I didn't notice any precum. He came on my chest after giving him oral. Now, I know this is kinda ridiculous but is there any chance any sperm entered my vagina? When he came on my chest I was sitting in the bed naked and the vaginal hole was completely covered and I immediately cleaned myself with baby wipes taking care of it to not slide down and then showered after. I'm so worried that some might have slid somehow and entered my vagina even though I know it was covered...

My period is due in 3 days and I wasn't worried until 3 days ago when I started brown spotting. I thought my period was about to come early but today it completely stopped. I read about implantation bleeding and that's what got me worried. Help??