I been with my girl on and off for 6 yrs.. I lost my Virginity to her and right now we are doing good.. I decided to tell her that while we were on a break that I had sex with 3 other girls and I caught genitial warts last year but I got rid of it.. I'm not quite sure if I got it from her or another girl. I just want to clear my chest about it. And also It's been on my mind if she might of caught something and if she had sex with other guys while we were on a break.. How should talk to her about this? Please give me any good ideas

Mention it from a long distance and then run the other way !

Emphasize your concern for her health. If it's possible you got it from her (or may have given it to her), then she should get tested. She may not like hearing that you were with 3 other women, but she has a right to know she may have an STI. It's the responsible thing to do.
Good luck!