Sudden FPS problems

[Concious]

I am running:
Geforce GTX 770M
i7-4800MQ @ 2.7GHz
16 GB RAM

I was playing the game for 5 hours without a single FPS issue(60 FPS) then randomly my FPS has dropped and I can't figure out why. I looked into the problem as much as I could and found that when at the pause menu or main menu I get 60 FPS no problem. When actually in game I looked at my FPS and found that the higher the value of "G"(maxed out at ~70 giving me ~15 FPS) the worse my FPS was and it turned red from white on the FPS meters. In game my FPS will fluctaute between 15-30 FPS, never reaches 60 FPS, and I have tried everything I know to fix this problem. Does anyone know what the "G" means and/or how to fix it?

[Whatzituyah]

Do you have smart v-sync on?

[Concious]

It was on before and after the problems. I tried all 3 options of vsync after the issues started and none helped.

[Whatzituyah]

Well I got nothing I have a problem myself I just don't get a fps drop in a certain place.