Recently: Game is choppy sometimes i.e. 44 frames per second, but, actually more like 20 or less

[solemn.9670]

On my main PC which usually gets 50-60 fps in most areas, and only goes down to about 40 in large WvW battles, I'm noticing it's a lot choppier lately and that it might say i.e. "44 frames per second" but it actually looks more like half that - very choppy.

 

Has not been an issue for me in the past. Haven't done any windows updates lately, I'm running Windows 8.1. Haven't changed anything major lately.