GPU keeps crashing. Please Please Help!!

[Spartin117]

My pc specs*
Cpu: intel i5-6600k 3.5 sky lake
MB: Z170A Gaming M7
Memory: G.Skill TridentZ DDR4-3200 8gb
GPU: AMD Sapphire Nitro R9 390 8GB
PSU: Corsair RM 750x
Cooler: Noctua NH-D15
O.S: Windows 10 64bit

I have had my pc for 3 years now. It seems all is good until I play a game, and even then I could get away with playing between 1 to 3hrs or it just takes minutes to crash it gose to a black screen and then my GPU fans kick on to max. I have to do a hard reset and some times my screen can't find what it's plugged into (HDMI cord is fine I tried 3 different cords with same effect) and all this happens after I play a game. I can wait awhile or remove the GPU and plug it back up and it turns back on for a while then rinse and repeat. I have applied new thermal paste to the GPU, and CPU cleaned out dust from fans, and heat sink fins to no different effects. My GPU peak temps are from 45-70c with a fan speed set manually at 5050 speed and med temps of 30-36c fan speed set to automatic, cpu is at 3.5 default and XMP is on.
When on load the CPU stays at around 40-45c when over clocked to 3.7 with a base clock of 100 which I benchmarked and ran stable for 2hrs.
I really do not know where to go from here and any advice or further question will be welcomed I'll try anything within reason.

[equisetum]

Start with a clean drivers reinstall (remove the current ones with DDU and install the newest) if it fails, the best way would be to take your GPU, put it in another PC and see if the problem is still there. If the GPU will still crash the PC that means that sadly it is dying and there is not much to do about it. If not, the problem is somewhere else. Might be a Motherboard issue. It is hard to tell.

[Spartin117]

Darn it, I was hoping that wasn't the case  I recently wiped my hard drives with a disk called Wipe drive which dose like 3 passes to wipe the drives, and I reinstalled windows and GPU drivers like a month ago when the crashes started more often. I guess i'll be using my CPU's integrated graphics soon, but none the less Thank you very very much for your help. 

[equisetum]

It is not a sure thing, it would be good to try a different card on your setup or test this one on another PC. Than you can be certain if the card is to blame.

[Spartin117]

Yeah I'll give it try and swap it out and find another PC to test it with.