Condom fail

Me and my girlfriend had sex, I had a condom on and finished inside of her, when I pulled out after, the condom was broken and barely even on. Her period tracking app said she was ovulating, and we got her a plan b an hour after, in case; even though I know it’s not likely to be effective and I’m paranoid, it feels so real to me that she is gonna get pregnant. We’re only 17 and I don’t know how to manage this if it’s true.