Its happened to me years ago, got tested a few weeks later, than 6 months down the line. All was fine.
The reason never to fuck barebackers with a condom, occasionally they do pop. Advice swap for a fresh one every 15 mins (if you can last that long).
Mine went on a longer booking, after 30 mins+,in the heat of the moment I never felt it go either. Prossie was really nice about it considering I shot my load up her.
Ive been off the scene for years, about time I got back in the saddle myself!