Sudden Fps drop and low gpu usage

[Masud]

My Pc spec,

 

CPU: i5 7500

GPU: Gigabyte RX 5700 XT gaming oc 8g

Ram: corsair vengeance LPX DDR4 16gb, 2400MHz

PSU:Thermaltake toughpower 80+ gold 750w

Monitor: LG 22MP68 1080p

 

Recently i upgraded my GPU to RX 5700 XT..As I was playing games(mostly The outer world and Metro Exodus), i noticed sudden fps drops. I was using FRAPS to monitor fps. I thought it was cpu bottleneck cause I have 3 years old 4 core,4 thread cpu. But then i switched to msi afterburner and rivatuner to see more details. My cpu usage was 75-80%, gpu usage only 60-65% and FPS drops to below 50. So it wasn't a cpu bottleneck. Then why my gpu usage and fps is very low..Any solution please. here is the sceenshot.                                                

 

 

Another Screenshot when gpu usage is 100%..

 

 

Also noticed that when gpu usage is very low(first screenshot), gpu power consumption is very low(below 100w) which is odd because 5700 xt is very power hungry graphics card.  Any suggestion....Please help.