I read this and I wanted to post something because I can relate to you very much.
I also had a very severe overbite...around 14 mm before braces and 11 mm after. I also had a very narrow upper jaw, one of the most narrow jaws my ortho has seen. Part of the problem for me is that I started treatment very late (when I was 20), so props to you for getting started on this sooner.
So, the first thing I want to say is don't feel afraid or compelled to say it's not an aesthetic issue. Yes, for me it was also functional...I couldn't bite, my jaw clicked, I can't close my mouth when I sleep...etc. But it was just as much aesthetic.
I've found that a lot of jaw people seem afraid what people will say if they tell them they want their jaw fixed for aesthetic reasons. Listen, your overbite is 14mm. This is not a case of vanity, this is borderline-deformity level, even if it doesn't look that bad because it's only one area of your face.
I was incredibly self-conscious about how my profile looks. It affected how confident I was, how outgoing I was...because I always felt like that's what people were looking at. And you know what, it doesn't even matter if they are or aren't...because that's how I felt, and that's enough to affect your life in a negative way.
Getting my treatment started is the best decision I made. I had a SARPE (which widens your palate), and it already changed my life. I'm scheduled to have my oral surgery in a month. That's going to be the last step and I can't wait to fix this thing that has been troubling me and put it behind me once and for all.
Additionally, a studying psychologist, I am appalled that your doctor did not treat you as someone with a valid reason to be upset.
So again, if this is something that is affecting you negatively, your life, your personality, your confidence, your self-esteem...I say take charge and fix it.
The only thing I regret is not doing it sooner and that I've lost so many years that I could have lived better.
My advice for you? Go straight to an oral surgeon. Regular doctors are greatly misinformed when it comes to facial issues. When I told my doctor I needed oral surgery for a referral, he thought I needed a dentist...
If the consultation is expensive, pay it and bill your insurance later. The oral surgeon will take care of creating a summary/argument for your case to show your insurance.