You are in a bad place right now; a broken engagement is like a death. In your case, I think it was worse. She loved you for so long and always forgave you but she grew up and you fought the responsibilities that come with age. My heart broke for you because even though your Dad and I tried to tell you she wasn’t going to put up with your actions forever, she finally had enough and you were shocked.
Three years later, you both are still alone, still hurting. So sad.
Get her back son, please. You are both stubborn and miserable, but you love each other. Do it NOW.