Had to reisntall Windows 8.1 and couldn't boot to Ubuntu afterwards.
then, i followed a tutorial to use Boot Repair. now, i see the boot screen to choose operating systems but the only option there is windows.

Windows is installed in a different drive than Ubuntu, so i didn't erase it from my computer.
the Boot Repair report is here: <http://paste.ubuntu.com/9937064/>

Any help is appreciated.