Gmod 10 not starting

Im probably not the first person to have this but everytime i launch gmod 10 its says gmod launching…Then it just pops up with an outline of window for a split second and then closes with no error messages.
So if there is any fixes for this PLEASE TELL ME.

Oh and p.s. I already tried reinstalling, deleting all data then reinstalling,and doing that -dxlevel 81 thingy.