sounds like some1 is in trouble

I am sorry you feel shell shocked but if someone does a 360 turn out of the blue there is probably a reason. It can be you or a host of reasons that might not have anything to do with you.

With out details it is just a guess. Not always when someone leaves you in the dust is it to hurt you. I have repeatedly seen people abandon relationships rather than drag someone they care about along for a miserable experience. Things like being sucked into a crime, going to jail, a catestrophic diagnosis, an illegitimate pregnancy, an assault that they just can't tell you about.

The important thing is when you revealed your feelings they didn't leave you in the dark forever in a day thinking that you had a future. Not a lot of comfort for sure. In time you will probably know why but if you don't getting your feet under yourself and moving on is where you have to focus. Good Luck.