How can I make her believe again?

Any advice will be greatly appreciated.

I was with my girlfriend for one year and eight months. We are both 27 years old. She was the love of my life. She was great to me in every way you could imagine. She found a house close to my apartment and asked me to move in with her. I was so excited to take the next step in our relationship. I was thinking marriage and children down the road. I’m a firefighter in a large city so I decided to work as much overtime as I could to help pay for things around the house. I lived with her for 7 or 8 days and worked four 24 hour shifts during the span. One afternoon I walked in and saw her crying. She told me that for the last 2 months she felt that there was something missing in our relationship and wanted to break it off. She thought me moving in with her would solve the problems she saw. She even told me she didn’t see us getting married. She gave me 3 days to move my stuff back out. My last day I was at the house I wrote her a page and a half paper explaining that our communication was lacking, I didn’t show enough affection as I should have, and that working so much gave me a bad attitude. I apologized and told her how much I loved her. Later that day she sent a text saying, ” I read your letter and I do appreciate it. I don’t want you to think it’s any of the little things that happened recently but I just know there is something fundamentally missing between us. That isn’t anything that either of us can fix. I am a better person for knowing you and someone will be very lucky to have you.” That was like a knife to my heart. I just know I could’ve fixed it if she told me. We had so many great moments together, and rarely encountered problems. I began no contact August 10th. My opinion is we didn’t talk about our deepest emotions enough and didn’t confront our problems with a constructive conversation. So how do I make her see this and make her believe we can fix this?

Jeremy