Try checking your temperatures with HW Monitor: http://www.cpuid.com/softwares/hwmonitor.html
It might be your CPU that is overheating.
Nope, CPU Max is 47c. GPU is fine as well, runs games at 31c
So yesterday games were working fine, booted it up today. Games are running slow again, and there isn't a restore point to yesterday. I haven't installed anything yesterday either...