Ive had that happen to a girl I was fucking and never knew until it was too late.
I left that girl a few weeks later and hooked up with another girl and the ex found out. Well about 2 months after the incident she calls saying she was pregnant and it was mine.....needless to say i was quite nervous as i didnt want a kid to that b*tch.
I found out off a mate that she was full of shit and wasnt pregnant. Apparently she was just trying to end my current relationship because she felt scorned.
Needless to say she got her own back in the end when some chick smacked her around at some party she was at for the shit she done
