Video card faulty?

To start off here are my specs-

Amd fx-8150 Socket AM3+ (942) Max TDP 124

ASUS M5A97 LE AMD970A AM3+ USB3 SATA 3 MB

RAM - Corsair vengeance DDR3 1600 mhz 4 x 4
Channel- Dual

Video Card- EVGA NVIDIA GEFORCE FTW GTX670 2GB GDDR5 PCI-E

Windows7 64-bit

Psu- XTREMEGEAR 800 WATT POWER SUPPLY

HD- 2TB SATA III 6GB/S 7200RPM 64MB CACHE 3.5" HD

Cooling- CASE FAN 120 MM x2
ASETEK 510LC 120MM WATERCOOLER

Every game that I play (ex: Dead Island, saints row 3, chivalry, Shogun 2, WoW etc.) I have an insane amount of fps changes. I keep a program open that allows me to see my video cards gpu/memory usage/temp/fps when I am playing a game. Sometimes it would same that my card is using 15% of its gpu and I am getting 10 or below fps and then other times when the gpu usage is at 50% and above I get 100-300 fps all on ultra settings. When I change the settings to low I get the same results. My video card has the latest drivers from nvidia and I even flashed my bios to update it. Any idea + any help??