Computer is loading extremely slow

[Kiweezi]

PC specs:
Cpu - Intel core 15 4690k
Motherboard - msi z170 krait edition
Ram - 2x4 ripjaw g-skill
Gpu - nvidia gtx 970 4gb
Storage - western digital 1tb HDD

For the last week my computer has been getting progressively slower. In that it's perfectly fine with every game but will stutter for a second or two. But the main problem is that everything on my pc takes forever to load, and I mean forever. It literally takes longer than my 5 year old Lenovo laptop. At first I thought it was one of those stupid updates from windows that takes up a ridiculous amount of disk but after completely disabling the updates all together, it still runs terrible. Just as another example, if I go into a game in overwatch my gun and sounds won't load in for about 5 mins into the game and when it does finally work, it freezes every few seconds.

I'm not too bad with computers and I checked the hard drive with crystal info and it was completely fine

Just kind of want any kind of ideas for troubleshooting and fixing it

Thanks in advance

Edit: ran disk defrag last night, only reached 64% complete in 8 hours. It was only 1% fragmented. Booted in diagnostic mode, computer will no longer get past the sign in menu and using shift + restart won't bring up recovery, neither will any function keys on boot. I'm stuck, really stuck

 

[hang-the-9]

First step for a slow system that takes a long time to load, get a new hard drive (SSD is best), install clean Windows on it. If you want to save some money, try a clean Windows setup on yours, but I have a feeling it will act a bit funny even then.