What if we don't get back together any time soon?

My boyfriend and I have been dating for 6 years straight, and just when he was going to propose to me, I broke up with him without knowing that and I drove away from him. I felt uncomfortable that he spent time with the new girl. Now that it's been 3 weeks since that happened, I've tried so much trying to get him to take me back, but he rejected me all the time. Now he is dating the new girl, and I don't know what to do. Just yesterday he mailed me his proposal ring, engraved with 'till death do us part'. He wrote on a post it note one word; 'longer'. I've tried talking to him but he won't budge to give in. He is going away elsewhere and staying there forever with his girlfriend.