I am going through the same thing. I know how you feel. My significant other emailed me one day and said he was moving out that day. I never knew why, he would not tell me. We never disagreed. I felt crushed my world had fallen around me. 4 weeks later he said he was in love with someone else. I couldnt understand how he could fall so fast when he gave me an engament ring at christmas this was March.
Each day it gets better, you cry less, but still some days more than others. I cleaned out of my house any thing that reminded me of him. I began to exercise to easy the stress I was feeling.
You learn to love your self, and you cant fix your partner, Its not your fault. It is his unability to cope keep a commitment. You are better off even though the pain is unbearable.
I couldnt eat or sleep for weeks, I still cry every day. Medication for Depression helped. But when I am alone I cry keep thinking everyday he will come back.