4 years good relations then fight because of kiss incident but wants to marry!

[yatinkumar]

Hi all,
i had a very gud relationship wid my gf for 4 years. Then bcoz of some dispute v ver parted fr some time. During wch a third guy entered her lyf. They dated hugged and kissed. This incident had turned me mad and v again came closer. Nw c is sayin me that c wants to marry me .. That all was jus temporary thing. N i belive her wht c says. Bt the nly concerns is i m very much afraid of that incident. Jus keep on thinking abt the kiss.. Please advice me wht should i do to make our relationship again to position where it was some time b4