Nothing personal, but you have to accept some of the responsibility of this situation as well. You can't help how you feel, but you are in complete and utter control of your actions. So things weren't going too well so you decided to have a "break". For those that aren't experienced with this, a "break" is a nice way of saying you guys are breaking up. It sounds like she wanted the "break" and you fell into the trap of clinging to her and hoping it would work things out. She wanted the "break" because she wanted to go out and explore her options while keeping you hooked. Even if it annoyed her to hear you text and call her, she enjoyed the attention. It was an ego boost for her.
So things weren't going well, she didn't want to even speak to you....and you got an engagement ring? Honestly, what could that have truly accomplished? You get an engagement ring when things are going so well together and you are growing together every day to the point where you both don't want to spend your life with anybody else. However, it's a two way street, and it's not a smart move if she wants a "break" from you. I think if she said yes, you would have regretted it anyway. It was a relationship based on a broken foundation. I think you wanted to believe that you could fix things magically, but there is no magical or quick fix. Dating somebody else right away wouldn't fix things for you either, although her dad told you otherwise.
All you can do is take this loneliness like a man and trudge on without her in your life. You are madly in love with her, but a proper question for you to answer would be: Why? Are you in love with who she WAS? The person that you dated for 5 years before things went bad? Because regardless of how it was then, that is not how it is now. She is not that same person. She is downright nasty to you. Maybe you feel like a failure and you deserved it, and maybe you did, but the fact of the matter is being with her right now would not make you happy. It would take away the pangs of loneliness and desperation briefly, but when you discovered that she doesn't really care about you like she used to, you would be hurt even more. Hammer that into your head that you guys could not be together logically right now anyway. Do as cloud said above, and work on living your life without her. Once you can finally achieve happiness on your own, you will realize that you don't need her in your life and your confidence will attract somebody else that is new fun and exciting. Don't be afraid of what else is out there, and remember that everything will be alright.
You can't make yourself stop thinking about her and you will. All you can do is keep busy and get yourself through every single day without contacting her or talking to her or doing anything involving her. It's tough at first, but when you get her out of your system, everything will be easier.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.