I called him another guys name...

A few weeks ago I went out drinking. I went back to my boyfriends house to sleepover. He didn't go out drinking but he just wanted to make sure I was safe so asked me to come home once I was ready to leave. Well I asked him not to tell me anything I did or said while I was drunk and he has been very good and hasn't told me anything. Except for what he said to me yesterday.... we were fooling around and I kept saying jack come back like I was in the Titanic, then he said If you ever call me another guys name while we're having sex I'm done and you're leaving. Then I said I would and that I was just being a smart ass calling him jack from titanic but he said he knew that. Then I said there's only been you and one other guy I've had sex with and I wouldn't say his name because he's a piece if shit (my ex who abused me). Well then he said if you ever said that name while we were having sex like you did when you were drunk and you were sober this time I'd leave you. My heart dropped I called him by my exs name while we were having sex when i was drunk but I couldn't remember that. But I do remember him telling me while we were having sex that he couldn't have sex with me anymore because I was so drunk. But now I know why and I feel like a fucking terrible girlfriend. Idk why I did it. I just feel so terrible!