I want my girlfriend back. How do I win her back?

I had a Cuban girlfriend for four and a half years but we broke up about a month ago because she felt like we were going nowhere. She already wanted to settle down but I was always scared of the idea of marriage. It wasn’t until after our breakup that I realized how much she means to me and that I actually want to marry her.
I’ve been thinking about it for a while now and I’ve decided to swallow my pride. I’m going to ask her to take me back and when she does, I’m going to propose to her as soon as possible. She’s the best thing in my life and it was foolish of me to let her go. I never knew that a short romance tour would turn my life around.
Can somebody give me ideas on how I would reconcile with my ex? How do I tell her about my regrets? How do I get back together with my Cuban girlfriend? I need all the help I can get.

It may be a little too late, but 'never say never.' After over four years together there may still be some hope left.

My recommendation: For starters, try calling her or sending a text saying you want to talk about what caused the breakup in the first pace. (It could have been over something silly.) Send her little sweet notes or messages telling her how your life feels empty without her. (Everyone uses their cell phones for all communication. Do something different; send her a short, sweet message in the mail. Sending a copy of her favorite song would be nice.) You know they still use this method! Women also love little gifts like a teddy bear or flowers. Kick in the romantic side of yourself.