I5 2500k Lag! help please x(

OKAY so like.. a couple of months ago my pc could run anything low and get 60-80 fps with a Gts 250 & i5 2500k &, 8gb ram.
then couple months later when i played Arma2 - Dayz. It starts to get low fps spikes. Before i didn't get any lag spikes from it or any game such as Splinter Cell Conviction it was 65 fps for like 4 seconds then it goes to 25. Then it goes to 65 again then it goes to 25 again.... So i run the game and then opened Task Manager. I see that my CPU usage is 50% when playing DayZ, it doesnt seem like such a bad % so i thought my GPU might of fried or something.. So i went to go buy a Gtx 560 I rebooted and everything ran DayZ again on high i got 75 fps then started YELLING YESHH!!
but *** 5 seconds later it went to 29 fps then it goes back to 75. Idk why this is happening! So i opened my PC up and looked at the CPU and the Socket. the CPU seems fine. Perfect actually but one part of the socket has a weird color to it. kind of bright, but the pins are not damaged in anyway.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! WHAT SHOULD I DO!