I hit my girlfriend and she won't talk to me anymore? Why?

I wake up in the middle of the night and hear someone breaking in. My girlfriend was at her sisters house because she was helping her with her new home. Me being a amateur boxer for all of my years as a teen, I figure I shouldn't be scared to handle it myself. I walk in to the kitchen and feel someone coming up behind me. Quickly I swung around and accidentally punch my girlfriend. Mind you it's dark as h***. it turns out she just dropped a some gl vases and was going to go get the broom. I have been telling her how sorry I am, but she seems so scared of me. I love her with all my heart. We still sleep in the same bed but she doesn't let me hold her, and I can't sleep right without holding her. What do I do?