Your story follows a very common theme here, as has been pointed out by above members of this site. I too had symptoms of HPPD from the time I was about 15 until 20. I did a lot of drugs in high school and at some point ended up with visual snow, depersonalization and slight afterimages, all of which are standard HPPD symptoms. After I graduated high school I actually took it easy on drugs my freshman year of college and within a few years I was symptom free. I took a few hallucinogens here and there but was always careful in never taking too much. Well, six years later all it took was a single tab of acid and I was thrown into a world and experience I wouldn't wish on anybody ever in the history of man. It's really clear that you're in a position we all were at one time and ignored. Don't be like us and ignore what your brain is telling you. Drugs don't work for you and your body type. If you keep doing them you'll regret it -- guaranteed. And not only that, you'll regret ever being born. Life on this planet is the greatest gift imaginable. Don't take it for granted. Doing drugs isn't worth it.