Downloaded and installed new el cap upgrade, now my imac is stuck on boot screen and doesn't move for hours. Tried a whole bunch of steps. Not sure what else to do.

I downloaded the new El Capitan upgrade, afterwards I installed El Capitan, my iMac now does not move from boot screen. I tried to restart my computer after several minutes of waiting each time. I tried going into safe mode, I got stuck at boot screen. I tried waiting several hours after restarting my comp. I am now stuck and not sure what else to do, I do not want to reset to my last hard drive save... I have some files that I do not want deleted. Is there a way to fix my iMac?