My girlfriend has been leaving things unfinished lately.

My girlfriend and I (both 30) have a generally good sex life. We’re very compatible on our kinks and things and it’s always fun. Lately though, we’ve been doing our thing, and then she gets off and will ask if it’s okay if we stop for a little bit?I always say of course because I never want her to do anything she doesn’t want to do. Things don’t really ever start back up. Today was our first Saturday that we’ve had to ourselves. We’ve made plans all week to do things today and when the time came, she finished and asked to stop. Again nothing happen. We had sex last night were I did finish, but it was a date night and we were both drunk. Is there something I’m doing wrong? I don’t understand why this changed.