My computer is insanely laggy lately

[BigMacAttacks]

What could cause such horrible lag? First time on the forums, i hope to find an answer fast.
i have a i7-4790k cpu, gpu is a geforce gtx 760, my ram is 8GB, anything else just ask. and YES i reset my router, i have a computer background which is why this is blowing my mind. I made a short video showing the lag i have on ALL video games, i lag even when not on a video game https://www.youtube.com/watch?v=lpJI6nJdps4 my computer is 16 days old, i have all drivers installed even the motherboard drivers as well. GPU is up to date, Motherboard is up to date, i even uninstalled the GPU and reinstalled it, even went to an older version to see if i just had a bad version, and it still lagged on there as well. This computer is BRAND new only 16 days old and about 9 days ago it started this lag. I checked chrome downloads, and even my hardrive, nothing installed without me knowing and i have ran several virus scans with Defender and nothing has come up. Also this is a imgur showing the weird font problem im having with my computer that started 9 days ago as well http://imgur.com/kJuOPyM

 

[RARRAF]

I think its probably PSU or heat try cheek the temps

 

[BigMacAttacks]

I think its probably PSU or heat try cheek the temps

Brand new power supply and 42 degrees just checked in the bios

 

[striderdon37]

So it wasnt like this when it first ran?