Crazy stuff man. I can for sure relate to your experience. Last night I took two 4 oz. bottles of Robitussin Long Acting Cough Syrup and went through a similar ordeal. I went into a different dimension. That's the best way to describe it. Everything was black and I was just crawling around on the floor of this other world. I literally got lost in my own bedroom, which was in my brain a completely different place. I realized that I must be dead so I started to walk around and explore the new world I was in. Everything was very dark and I had to feel my way around, and the there were random lights all over the place that were the souls of some unexplicable things. As I was feeling around I realized I was touching stuff I knew was in my room, and realized I must be alive and just really REALLY fucked up.....which I was. I started to drift back to reality.
This was the most intense experience I have had on DXM. I agree that this drug is not something to think lightly of. It's best to use with other people around who know what to expect. I however have used it quite a few times, and have a good idea of what to expect, but as you can tell there's always something new to be seen, learned, and experienced on DXM.