Scarleteen

Alright last night was probably the scariest night of my life. My boyfriend and I were masturbating each other while standing up and while hand was in my pants he ejaculated. When he did that the sperm flew into the air and down toward my pants. It got in my underwear and reached the top of the vulva(where the clitoris is). I started freaking out so I wiped everything off with toilet paper. I don't even remember if i re used the same paper to wipe myself down there. After a little more freaking out my boyfriend went and bought plan B and I took it 2 hours after our little mistake. Now I know my chances are higher if I take plan B right away. However, I'm almost at the weight limit and I heard it doesn't work after or during ovulation (and i don't know if I was ovulating or not, I do know I was close). So, what are my chances of pregnancy if plan B doesn't work in this situation?