About 3 years ago in freshman year I was about to date this girl I really liked and we've already confessed feelings for each other. A couple days into the relationship I was hospitalized and was diagnosed with leukemia. She disappears; no text no calls no nothing. I waited for her but it was a hard time for me so I moved on with a new girl that I fell in love with and she stayed by my side through all of the chemo and radiation and bullshit she got me through it. After I got out of the hospital and my immune system recovers she ends up cheating on me and of course I break it off with her but eventually we just drifted together again. We go steady for almost a year and a half but she has had loyalty and attitude problems. She has this attitude of we do what she wants or else she fights until she gets it her way, it's not enjoyable and makes me not want to be around her. The guy she cheated on me with shows up one day at a party and she completely forgot about me and starts talking to him so I pull her aside saying I'm getting tired and want to go home. She wants to stay with her brother and tells me to go so me being trusting and everything I go home. I find out they had sex that night and have been talking the entire time me and her have been dating. I love this girl she was my everything and she was caring and sweet in the hospital but she turns around and stabs me in the back. I know it was right to leave but she fucked me up mentally I can't get it off my head every time I think of it I get so angry I pace around the house cursing out. I'm moving on but I have my moments where I have no trust and I'm insecure and I'm worried that if I trust someone I'll get hurt again. What can I do to stop being so insecure?