Should I add RAM to my PC?

Hey community, I think I'm in need of some more RAM...(games run sluggish at times and internet is fine)

So I have a home built PC with the following specs/parts
ASUS Sabertooth 990FX motherboard
16gb Corsair Vengeance DDR3 SDRAM
EVGA 960 graphics card
H100i V2 liquid CPU cooler
Corsair AX860 PSU
AMD FX-8350 8-core 4.0ghz processor

Or could my issue be that my OS is on a HDD and my games are all on my SSD. Would putting the OS on a SSD improve my game loading times?

I just recently...

Should I add RAM to my PC?