Windows 8 sleep mode problem?

So I've had my computer for about a month and I had the power settings to turn off monitor and computer to sleep after 5 minutes and it worked flawlessly. As of yesterday now though, after the 5 minutes is up the monitor will shut off but the computer wont initiate sleep. The computer stays awake, and only about %20 of the time it will actually sleep now. I can manually make it sleep by clicking on sleep but it won't auto sleep anymore rarely. I haven't changed anything on the computer at all, why is it doing this and how do I fix it so that it sleeps like it should under power options? Thanks.