Plan B

Has anyone gotten pregnant after taking plan b? 
I took it a couple hours after having had unprotected sex and I got my period but it started off weird like it was just a spot for 2 days and then increased and got lighter again so pretty normal but idk it just wasn't like my usual period but that may be the plan b's doing. I'm now having like weird slight abdominal cramps which I don't normally experience after finishing a period. Maybe I'm just paranoid but I just wanna ask to see if anyone has had any problems with it