About two days ago (About 3 am on September 30), my boyfriend and I had 'sex' for the first time. It was also my first time ever. He never actually put it in all the way, there was only a little pain and no bleeding, and it didn't last long at all. He didn't ejaculate inside me either, and I'm unsure about precum. We did stay naked for a little while but still, he never ejaculated. We didn't use any sort of protection and he told me he was infertile. What are the chances I'm pregnant? I have a certain level of anxiety so I'm stressing out. I had some brown stuff on my underwear shortly after but then was fine, but noticed some slight pink stuff on toilet paper after I wiped (Both #1 and #2 sorry if tmi) once today but there's been nothing since. I did take Plan B less than 24 hours after it happened to hopefully be safe. And today, I have some back pain and some other weird feelings in my stomach/uterus. I'm not supposed to have my period for another two/two and a half weeks and I've had some of the stomach things before but of course I'm freaking out now.