Just stay strong Passion, do things you have passion for! (Briljerar med svensk dryg humor :3) I am also feeling really depressed now and then, but for that i'm going through kbt which really helps! You should really see a shrink (If you haven't done that already) and just get it all out, they might not understand hppd but they do understand deppression and anxiety.
And the 2D part i can really relate to, i had that a while back but i kept my self really occupied with school and friends and all of a sudden it went away. I think it (depersonalisation) has a REALLY strong connection to anxiety. Right now i have almost no anxiety at all and my visuals are very mild, i feel like i don't have hppd but i do.
You still haven't had hppd for quite a time and when i had had it for as long as you have now it was just horrible, it really eases up fast and you will soon experience a habitable bassline of symtoms