Help me fix my PC, RAM doesnt show

[A7XX]

I have 16gb of HyperX Ram memory  2×8 DDR4 2800MHZ, My system shows only 8gb of memory. This happend to me a year ago, what I did then was tried to swap channels clear cmos clean the pc, update the bios, I even tried to use different type of memory from my friends PC but it still showed 8gb, a little while after I gave up on trying to solve the problem, I open my task manager and it was reading 16gb, I dunno how, I dunno when but somehow it was reading the correct amount of memory. Yesterday I was looking up something, and I had lots of Opera browser tabs open, and my PC started slowing down and the screen turned black for a minute, and my Opera crashed, so I opened task manager and the reading is back to 8 GB of ram again, its driving me nuts, can anyone help?

System Specs:

CPU: Intel Core i7 5820K
Cooler: Noctua NH-U9S
MotherBoard: Asus X99-A
Ram: HyperX Savage Black 2×8 DDR4 2800MHZ
GPU: EVGA GTX980 superclocked ACX 2.0 4GB GDDR5
PSU: SeaSonic G-750 750W Gold
SSD: HyperX 240 GB

[A7XX]

BTW, My ram was running at 2133mhz I didnt have any xmp running at all

[A7XX]

help

[A7XX]

any1?