I had sex with a girl, i used a condom, and came inside her. she has been missing her period. what is the %.

Hard to say: Listed failure rates for condom use run 20% per year with variation based on how they are used.Poor fit, or intercourse prior to covering up increases failure rate, since both can allow sperm to enter the vagina.Good fit and conscientious use decrease failure rate. If she is really pregnant (test) paternity can be assessed as early as 8 wks using a non invasive NIPP study.