FPS has dropped a lot in the last 4 to 6 weeks.

Hello, I have a strange problem regarding the FPS of the game. About 4 to 6 weeks ago i used to have around 80-100 FPS and 50-60 in Dalaran but now I have around 8 in galaran and 40 in general. This little problem is affecting my raiding by a fair ammount and it's frustrating.
Build:
CPU: I7-4700HQ
GPU:GeForce GTX770
Rams:24 gigs
With this build I should be able to sqeeze a lot more FPS than 8 in Dalaran. If you had this problem and managed to resolve it could you pelae tell me how?

check if vsync is off.

sometimes when chaning from fullscreen to windowerd and vice versa vsync gets activated for me.

I also keep it turned off. It is not from that, and I did not do any changes.

Delete your cache folder, it probably won't return to your previous FPS, but it'll be a bit better.
Also did you install any new addons? Try disabling them all and see if it's better.