I'm in a relationship with a native speaker too (I'm American, she's Chinese), and am actively learning. I talked to a lot of couples and some people have patience to teach and some don't. It's nice though that couples are close enough to correct each other and help each other out.

I had a friend learning French that was French teacher, and she gave up after two sessions, not having the patience.

Actually, I just started working on an app to help couples improve each other's languages. You're pretty fluent already, I wonder in what other capacity's your girlfriend who is an English teacher helps you!