Plan B

I had sex this week and the condom slipped off in me. My boyfriend thought I should take some plan b but he got an off brand called aftera. I took it a few hours later that night and started getting cramps the next day. I am supposed to get my period but I haven't gotten it yet. I'm still experiencing cramps from when I took it but no blood idk. My bf thinks ill be fine but I can't help but be a lil worried. Has anyone taken this before? Is this normal?