Scared of getting pregnant

I normally use the rhythm method to avoid pregnancy. I am 39 years old, my period has always been very regular. This last period was no different but on the 18th day of my cycle my boyfriend came inside of me. Normally I would not worry but it just happened that I had felt a pain in my ovaries that same day. I have always been very in tuned with my body and that pain almost always on my 14th day which is when I think I am ovulating.

So now I am scared and don't know if J should go buy the morning after pill?

What do you guys think?