Mythos. I don't know you and I'm not in your head but you're clearly a bright person and I'm hoping ... really hoping that you'll seek out the loving people in your life for support and help. Given time, it does get better. My 20s were a very rough time but each decade got better and better.
Oh, I thought You were honestly ending it, so why not throw a hail Mary and if it doesn't work, You leave guns blazing.
I wish You the best either way. <3
Edit: to clarify my beliefs about HPPD, I think it is 95% psychological ( as someone already claimed it here ) especially if it was induced by a bad or weird trip. The visuals aren't a problem, I had them before and I didn't care. The problems need to be sorted out on a subconscious level. I mean isn't it weird that the psychological problems resemble PTSD?