Same hardware reserved problem...AGAIN!!

Ok, I had this problem for a few months around the start of this year. My system is

Ok, I had this problem around the start of this year. For some reason, out of nowhere, I had around 5.9 of my 10gb of ram actually usable. I had not ever messed around inside the pc, and had never reset the ram sticks. After seeing this, I reseated all the sticks, the pc booted with a single stick on every slot, but I still could not utilize the entirety of my memory. So around March of this year I decided to buy an this ram stick: https://www.amazon.com/gp/product/B005T63BJM/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

For some reason, after putting in the new stick, I had all 18 gb usable now. I have no idea, but after blowing the dust out of my pc yesterday, the system was stuck on the hp logo, and would not start. So I checked all the plugs in the computer, made sure the ram was all seated properly, etc. It had the full 18 gb then. This afternoon however, I load up, and see I only had 10 gb usable. Weird. So I left my 4x2 ram sticks, and the 8gb one out. Now I only had 7.8 usable. Crappy, so I put the 8gb one back in, took the 2gb one out, and resetted. Now it had like 5.8 usable. I then put the 8gb one in the 2gb one's slot, and the same result. I put everything back to their original state, and now I still only have 7.8 usable

I have reset the BIOS to defaults, used memtest, and everything is fine, set my max memory to 18 gb, then unchecked, no results. I'm at my wit's end, can someone help me?

Model

Brand
HP

Series
ENVY

Model
h8-1534 (H2N64AAR#ABA)

Processor
AMD FX-6200 3.8GHz

Processor Main Features
64 bit 6-Core Processor

Cache Per Processor
6 MB L2 Cache

Memory
10GB DDR3 1600

Storage
2x3tb Toshiba internal hdd

Optical Drive
SuperMulti DVD Burner drive

Graphics
AMD Radeon R9 380x 4gb

Ethernet
Gigabit Ethernet

Power Supply
Corsair C600 psu

Operating System
Windows 8 64-Bit

Motherboard

Chipset
AMD 970

CPU

CPU Type
AMD FX-Series

CPU Speed
FX-6200 (3.80 GHz)

L2 Cache Per CPU
6 MB

L3 Cache Per CPU
8 MB

CPU Main Features
64 bit 6-Core Processor

Graphics

GPU/VGA Type
AMD Radeon HD 7570 2GB

Memory

Memory Capacity
10 GB DDR3

Memory Speed
DDR3 1600

Form Factor
DIMM 240-pin

Memory Slot (Total)
4

Maximum Memory Supported
32 GB

Hard Drive

HDD
1.5 TB

HDD Interface
SATA

HDD RPM
7200rpm

Optical Drive

Optical Drive Type
DVD Super Multi

Front Panel Ports

Front USB
2 x USB 3.0

Front Audio Ports
2

Card Reader
15-in-1 multimedia card reader

Back Panel Ports

PS/2
2

Video Ports
1 DVI, 1 HDMI, 1 Display Port

Rear USB
4 x USB 2.0

RJ45
1 port

Rear Audio Ports
6 ports

S/P DIF
1 port

Expansion

PCI Slots (Available/Total)
1 x PCI Express x16 (Gen 2.0)
3 x PCI Express x1 (Gen 2.0)
1 x PCI Express mini card (for half-length add-in cards) with USB connector