Help! Wish to win back the love and affection of girl friend.

My girlfriend and I started dating 5 years ago. We are both foreign students from different countries. We are in long distance relationship. She lives 370 miles from me. We visit each other at least once a month, usually twice. We spent great time together during summer,winter,spring breaks. Things were great until last year. I know I had become stupid and may not have supported her as much as I should have.
In winter she went to her home country, and a guy kissed her when she was drunk. When she came back she told me thatshe likes that guy, but she loves me. We broke up so she could have her space to think. I tried to use no contact, but she called me and told me that she hates it when I don't stay in touch with her and she wants me to be work harder for her. I could sometimes feel that she really does love me but sometimes she was cold to me.
Recently I went to her place, and stayed there for 2 weeks. I showed her I am a more caring boyfriend, I took her on dates, cooked her nice meals(which I didn't do much before). She cried that she was selfish to break up with me. She told me that we are back together. She made me feel loved again.
My problem is that even though we are back together, I am scared that she might leave me again. I would like to make the bond stronger between us. She sometimes acts aloof. She is different sometimes. I am giving her space. Taking things slowly. I just wish we could be truly be in love again like we used to. I have improved myself in many ways.
I really need some ideas on how I can win the heart of my love, so I can keep her without being nervous, scared of losing her.
I sometimes feel really down, even to the point of killing myself.
I need help, really appreciate your ideas.Please help! Thank you.