Trippy breathing exercise experience

[Topann]

Ok, to start I was following along to a breathing exercise video. The breath work was very relaxing to begin with, long and controlled breathing seemed to ease my mind and allowed a trance like state to come over me. I remember feeling my heart beat and the blood pumping through my chest and having a real sense of how amazingly complicated our bodies are to operate so autonomously. After that, a very subtle yet extremely strange feeling came up. Tightness in my chest, nausea, dizziness, and a sense that something was wrong. So much so that I had to lay my head down and eventually fell out of my chair onto the floor. This is really where language fails me, but the best I can say of it was it felt like I literally died and I lost all sense of time. Whatever this thing was, there was no distinction of anything but it also felt like nothing and eternity all at the same time, idk. 

I feel very confused as to what to do with this experience and I also feel extremely shaken up. Just looking for some additional perspective.