Download MSI Afterburner, it has a graphical display detailing a load of things, two (I guess technically 9-10) of which are your CPU usage(s) and GPU usage. Download that, give it a whirl on whatever you're attempting to play and look at specifically--which cores of your CPU are getting stressed, and if they are hitting 100%. If any single core is getting close to/is at 100%, it's an issue with the CPU binding your FPS. If the GPU usage is hitting 100%, it's an issue with your GPU.