It is not surprising that she has a new bf. Given her desire to get married and have children, she was likely dating many guys if the opportunity presented itself. When you don't spend regular, quality time with your gf--you are giving the competition all the opportunity in the world to take your place.

I would talk to her. If her current bf is not meeting her needs, you might have a chance to reenter the picture. The fact that you left her for such an extended period of time will be a strike against you. The man I married wanted to spend time with me every single day and we constantly held hands, kissed, etc. Some women need this.

PC is a good place to learn more about your depression and anxiety. Perhaps that is the issue that you need to concentrate on seeking treatment for. Good luck.