Really liked reading this, made me wish I had a similar experience. Unfortunately, my parents never exposed me to music so my journey into music started really late.
I seem to have had "phases" like what you describe too, a couple of years back alt. rock was most of what I listened to with stuff like Muse and The Killers being some of my most listened bands, but now I just listen to a bit of everything I like and rarely stop listening to some band altogether.
I find your experience with post-rock amusing, because I got into it in the exact opposite personal situation as you. It was in a rare period of mental clarity and where I "found" myself (as opposed to your "lost years" haha) that I started listening to Explosions in the Sky. From there, the other big names in post-rock followed and before I knew it I was a huge fan.
Good luck in your music career.