A wall of energy slammed me back during meditation? What was this?

2 years ago, I was meditating for about 2 hours a day and was rapidly transitioning to a higher vibration when all of the sudden, I was slammed back by a force of energy back into my chair. Since then I havent been able to get as deep into meditation as I did before then. Im not sure what happened, but feel some kind of a block happened. Has anyone else experienced this or know what happened?