Breakups suck

So about a month ago I broke up with my girlfriend for the second time. I didnt see a future anymore and in hindsight through this last month I have realized that our relationship wasnt as great as it shouldve been. Now I made so many promises of marriage to her and a wonderful future so breaking up was the hardest thing that I had to do and I fell into a deep depression. I knew it was the right decision but I still was just hard on myself. Not to mention I found out a few days after the break up she started talking to a guy again who she had talked to the first time we broke up and she liked him. He is in the military and they have actually never met in person. I was devestated that she could move on that fast. I am happy for her I mean I cant be mad because I was the one who broke up with her but I feel just like completely worthless. I wasnt enough for her and she found someone who did I guess. I also found out she had been thinking about him during the 2nd part of our relationship and that she new all the problems of our relationship and never communicated with me so she was pretry much ready to move on. I was hurt and said some bad things to her which I have apologized. I have apologized for everything. I did not have a backup plan, I did not want to break up but it had to happen. I was not ready to commit. I dont want anyone else tho, I dont want a relationship. I just want to focus on myself but I havent been happy and I just want to move on and be happy like her