Condom left inside after sex

Alright guys so I had sex with my boyfriend night before last and when I got back from going to the bathroom he was looking everywhere for the condom. Turned out it had stayed inside of me after he finished as we had stayed in that position for a while after. The same thing happened in December too and I had my period days later. Im not yet on birth control because Im waiting for my health insurance to kick in so I can get and IUD and Im wondering if I should take plan B. My period is in 2 days so I know I wasnt ovulating but still, Im not sure if I want to risk it.