Fps went seriously donwhill after sometime

[dulzonpirus]

so I just got my new pc on November 2016. when I first got it, I can pplay CSGO with very high fps. 200-300+ fps. I also play League of legends. When I started playing, I got 200+ fps too. Late December everything started going downhill. My cs hit 60 and sometimes goes below 30. same goes for League. started 100+ fps, then goes to 80 to even 50- if there's a teamfight. When I played Shadow of Mordor I saw the my benchmark was around 100+ fps. When I played it was like 50-. So I was wondering if the problem was with my cpu or the monitor.
I'm very new to computer things and I kinda threw away my list of the components of the computer but I can remember that I got
-GTX 1060 Strix
- 8 GB of RAM
-Processor Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz, 3501 Mhz, 4 Core(s), 4 Logical Processor(s)
-System Model= H170-Gaming 3

Now my monitor is very old. Its Samsung and got 60 hz refresh rate. I was wondering if there's something wrong with the cpu or should I change the monitor. Please help!!

 

[Dragos Manea]

Downlaod and install gpu-z and at sensors tab see what usage you have when the computer is idle(does not do anything). You might have a miner.

 

[Zerk2012]

Download and run OCCT and check your CPU temps.

 

[dulzonpirus]

Downlaod and install gpu-z and at sensors tab see what usage you have when the computer is idle(does not do anything). You might have a miner.

it shows that the gpu core clock is at 13 MHZ and the memory at 202.5 MHz
I'm not sure of what these numbers and what does it mean. And if there'sa miner, how dpo I remove it?