PC Crashing and Freezing

My Rig: Processor: AMD FX-8350 GPU: GTX 770 RAM: 8GB/16GB RAM PSU: EVGA 600W Motherboard: ASUS M5A97 R2.0

My Problem: My PC has been playing up for over two months now, and now that I have a bit more free time I'm trying to fix it so that I can use it properly. The initial problem was that when I was playing games such as Civ 5 it would either freeze or crash my PC. When it froze I had to turn it off via the power button; but when it crashed it would show no BSOD and once it turned off it would restart itself and then show BSOD such as WHEA Uncorrectable Error and System Service Exception. More recently I've been playing Overwatch which will occasionally crash with BSOD including: WHEA Uncorrectable Error (most frequent) System Service Exception (2nd most frequent) Memory Management (3rd) Faulty Hardware Corrupted Page (4th)

So today I installed a 600W PSU (which had been 430W previously) and 8GB of new RAM after finding errors on memtest. I then ran BF1 which still caused a BSOD and started a restart BSOD loop. Currently I have my old and new RAM installed (16GB total) and I then ran BF1 again which ran for a lot longer, but then froze my PC and became unresponsive.

What I have tried to resolve the problem: I have tried resetting my PC (keeping my files) but that gave an error so did not complete. As stated above I ran a memtest on my old RAM which came up with 14 errors. I have previously reseated the CPU fan and applied some more thermal paste to see if it was a heat issue with the CPU. I have checked the the Nvidia drivers are up to date and Windows is also up to date too. I have not recently tried to reseat the GPU so will do tomorrow.

Thank you in advance for any advice you have.