pregnant?

so I had sex 4 times on friday. once with protection and 3 times without. he finished 2 out of the 3 times without the condom but he pulled out. the second time he finished he didn't know he was going to, so he pulled out really fast and finished on a blanket. I'm scared he might have finished inside of me but he doesn't even know if he did. should I be scared? I get my period today and I've been on birth control for 3 months. I was thinking about getting plan b, should I?