Paranoid Virgin Help A Newbie Out

Ellie • Just a Paranoid virgin
Hi I am 17 years old and I am a Virgin and a very paranoid one... I have been on the pill since I was 12 because of medical reasons and I am very reliable and I haven't missed a pill in months. I also have a lovely boyfriend of 9 months. We have been discussing loosing our virginities to eachother. The other night we were cuddling and he rubbed his penis on the front of my vagina. Nowhere near the actual vaginal opening but not on the public mound. He had already ejaculated about 15 minutes before and was completely clean and he only rubbed it on me for maybe 20 seconds at most. Again there was no penetration and no contact even close to the opening there was no precum as I could see and he swears there was none as well as the whole instance only lasted for 15-20 seconds. The day before I was going to a sleep over and took my pill 4 hours early but other than that I was 100% consistent within the hour and not missing a pill for atleast 3 monthes. What is the likely hood that I could be pregnant. The next day I think I got my period also (I have a very very light period so light sometimes it seems as if it doesn't even come) what is the likely hood that i could be pregnant?