Love lust split and ED?

I’ve had this problem for my whole adult dating life and I’m desperate to find out if anyone else has had similar issues. When I’m hooking up with a random girl or even a girl I know doesn’t want. Relationship, I can get hard as a rock and never worry about performance. I can just have sex with zero issue. The opposite holds true when I’m with my partner when in a committed relationship. After a few months I slowly lose the ability to stay hard and get hard. It’s gotten to the point now that I need to jerk off alone to release tension because I cant get it up with my partner. Why do I always lose sexual interest in long term relationships? Why can I so easily get hard for someone new or someone who just wants to have sex, but lose the ability with my girlfriend? It’s extremely frustrating and has caused many issues in my relationship.

Has anyone experienced anything similar? A psychologist named Esther Perel (she’s awesome… watch her TED talks) calls it the Love-lust split.