-ExcaL- :
Natan_3 :
Is your FPS dropping as well? It's not a problem to your core clock vary sometimes, what you need to worry is your performance ingame
Yes my FPS drops along with the core clock
check your processor temperature, and check GPU, CPU, RAM and disk usage. Your core clock can be dropping due to CPU bottleneck or you're not providing enough RAM to the game.
Also tell me all of your computer specs