Only using 10% of cpu, low FPS

I have no idea why but I did everything rem's optimization guide told me, whenever i would switch to performance power or anything thats supposed to boost my fps my FPS literally does not go up a single bit, when I checked in task manager only 10-20% of my cpu is being used, why is that? I feel like my fps literally went down over the span of a month from 300 to around 180.