Character progress loss

Help please!
Today i had some WoW technical problems and had to redownload the game but when i did my character went back in time for like 10 hours of playing. from 26/27 level back to 15. same with all skills, money etc. what could've happened and is there a possibility to get my character back in previous state?

Make sure that you are checking the same character at the same realm.
Characters are saved server-side, so any problem within your client will never change your online content. Crashes might take back some of your progress, but only few minutes progress (up to 5min).