Sharing Our Innermost Thoughts

I never had any girls friends in my entire life until I met her she was my first Friend who cared about me after my mom she never left myside when I needed her but I never actually cared about her very much then after 4 years we graduated and we moved in like we were sharing apartment and then slowly everything turned so quickly. It’s been 13 months .
We have never been in a committed relationship it was like benefits but we truly cared for eachother I’m in love with her but she’s not . She’s has this guy who’s looking after her they don’t have relationship or benefits but he truly cares for her trusts her and leaves her for her own will . He even let me stay with her so she respects him. Everything is so good we were hiding our benefits from him . But I think he knows but he asked . So recently my father got passed and I was a mess she was with me all the time . She’s trying to cheer me up and telling me to what to do how to react and everything and after few days I came back and I bought my sister to our flat to live with us she agreed for that also . But soon I found out that she slept with another man while I’m gone . Not only that she had sever affairs back then. I foun their chats and photos in her mobile . Which she never told me .
So I confronted her she was like it’s my business and I never committed to you or anything and I had my freewill how can that be .?? We have been living for over a year and she had a guy over like 2 times without telling me . After that fight I thought of never getting back with her but after 2 days I went to her ans sleep beside her and she’s like okay .then again we start for good this time I wanted to change her so I never left out my sight . I loved her truly . But then again she went out with a guy for shopping he’s her inter classmate even though I said I wanted to go . What should I do …???