FPS drop in all games

Hey,about the last 2 weeks I have a problem of FPS drop in all the games,it doesn't matter whice game I play,there is FPS drop.it started when I had performance degradation and also FPS drop,I fix it by closing unknown background program that use a lot of the CPU.The FPS in games back to normal but there is still FPS drop,it's happens every few seconds and the FPS drops by 20 and more.The temps are ok,the lastest driver is installed on the computer,I also try other drivers but I doesn't help.everything worked well until now so it's not hardware problem.
I really tried everything and I don't know the reason for the problem.
please help me.I'm really appreciate that.
I didn't mention that the FPS drops every few seconds,and then it's back to the normal FPS.so there is situation that every 3-5 I got lags so I can't play normal with this problem.
 
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