How effective is plan B?!?

We had a little accident. Poor planning, heat of the moment. He finished in me before we even realized, which again I’ll admit was a bad idea in the first place.

We ran over and got Plan B and I took it. I’m just really nervous. I normally discharge a lot and nothings really happening down there right now. I was cramping yesterday but today, nothing.

Should I take a pregnancy test? Any expertise? I’d really appreciate it