HELP PLEASE?!? NEED ADVICE ASAP

Maya

My boyfriend and I had sex about an hr ago and it’s my second day on my period. I’m nervous because the condom broke and he was still inside of me at the time. We pulled out right after since I heard something. He didn’t finish but should I be worried since I don’t know if there was pre cum or not. I know my chances on getting pregnant are very low but should I be very worried and buy Plan B?