Non starter in bed, is it my fault ?

ok so i met a girl, we got on really well and had loads in common etc etc but although she was real sweet she admitted on our 1st date that she`d never been faithfull to anyone before, also she told me how many guys she`d had sex with (lots of)this set alarm bells ringing, naturally, but after a whil this didnt seem to bother me at all until the 1st time we went to bed together, then i cudnt stop thinking about the amount of guys who alrealy planted their flag lol, and it completely threw me off and i wasnt able to have sex with her, i felt so bad about it, it happend 2 times more before she put me out of my misery and ended it, but i feel like i screwed up something really good over my own insecurities, anyone had a similar experience??