Help!!

I had sex last night and when I was riding my bf I guess the condom came off inside me and we kept fucking for another maybe 2 minutes. Then he pulled out to cum on my tits and the condom was no where to he found. So I went to the bathroom and pulled it out and it was pretty far up me. There was pre cum in the condom. My stomach hurts a little this morning and I'm cramping a bit. My first day of ovulating was yesterday too! Should I take plan b? I'm not on BC.