Help! FileVault installation problems!

I have a MacBook Air (13-inch, Mid 2011) running Yosemite with a processor: 1,7 GHz Intel Core i5, and 250GB.

I wanted to update to El Capitan, and accidentally turned on FireVault encryption, and after approximately 2 hours the encryption process is saying there are 332 days remaining, and the bar showing process keeps jumping between 33% and 100%. Is there any way to sotop this process without damaging my disk and computer, as I do not have a backup.

My computer is currently running at significantly reduced speed.

How long will this process normally take? And should I turn it off if the process ever finishes? Have read that this will take an extremely long time as well.. So upset that I was able to do this by accident, as I have a lot of work to finish.

Please Help!