FPS collapse after 40 minutes of gaming

So after a failed oc to 4.5Ghz I went to 4.1Ghz on my cpu

I'm running my card at stock speeds.

After playing BF4 for about 30-40 minutes my fps go from 60-90 to 20-30...very bad.

Did I break something?

I already tried re-installing drivers that didn't help.

This only started happening after a BSOD talking watchdog clock timeouts or something like that btw.

FPS collapse after 40 minutes of gaming