Am I a bad friend?

So during summer I started dating this guy, he had a best friend that had a girl friend too, so her and I became friends. Well after a couple months both her and I became single, I was still cool with my ex for a little bit until I went off on him at a party when I was drunk(we made up and became friends after a month or so) but during this time I was friends with his best friends ex, well within the past 2 months I've gotten really close to his best friend ( my ex is in boot camp now so he doesn't know I'm close with him) well....him and I are now friends with benefits and really like each other....but we don't know if we should make it official, none of the ex's know (one of my close friends and his best friend, my ex,) My friend never wanted me to be friends with her ex in the first place, but as of right now her and I aren't as close as we were....should we go for it? Should we tell the ex's? Or should we still keep it a secret?