PLAN B (help)

Kenz
So my boyfriend and I had unprotected sex, he didn't cum in me, it honestly was just 15 seconds. I am supposed to start my period in 10 days but to be safe I'm going to take the pill. It's going to be my first time & ive heard horror stories about it. 
I've never been in this type of situation before so I'm freaking out lol!
 I should be fine?