I want to stay with her?

I met this girl a year ago since than we have been together. There was a guy who was her friend who aparently had something with her in the past. One day he sent me a pic of them kissing idk if it was old but still. After that i called her job and told their boss because they worked together. She first wanted to brake up with m but than she got mad at him but months later she was still talking to him i dont know i feel like they had something strong and that the only reason why she is with me is because he told me they had something. Also he only likes to spent time with her not woth her kid . She has a kid and i have a kid. I wasnt the best stepdad but at least i took her son everywhere we went.

We have been fighting about that friend of her over a year i love her . And she did stop talking to him but its like i dont trust her anymore althougj she has changed. One day i found out she came over his house .the whole day and she took three busses just to see him.