Cant play games fps drops. Just built my pc.

Gromeer

Reputable
Apr 5, 2015
8
0
4,510
specs
motherboard: ASUS H87M-PRO
Gpu: 750 ti ov/v1
cpu: i5 4430s
psu: corsair cx 600m
ram: 8 gig

When i play league my gpu usage is around 10% so i get like 40 fps while playing. When i play bf4 my usage is around 90% and i get a clean 60-50 fps.
when i play sc2 well i cant my usage is around 5%.

Whats my problem? Why do i get these random drops its fricking annyoing.