Been hacked

I've been hacked some point today in not able to change passwords never gave any details out to anyone anywhere they been thru sold anything tradeable in my club and took all my coins I never got any notification  to say anyone tried to log in to the account or anything I'm fuming don't know what I'm supposed to do I can't get on to change password or anything I've put money into the game n paid for the game itself which is annoying considering time and money I've put in this hasn't happened to me before but its been enough to nearly put me off the game and absolutely ruin my day what am a supposed to do?