FPS Stuttering When Downloading

[Tannersaurus]

Here Is my system build:

AMD FX 8320 @ ~4.2ghz

24gbs of RAM

NVidia GTX 760

MSI Gaming 970 Motherboard

So, whenever I download something or load a website on the internet I get FPS lag. Also, I don't get the internet speeds promised to me. I am connected to the internet through ethernet. Example: on my phone i get 90 down and 5 up but on my computer I get 20 down and 5 up. I don't know if i should buy an internet card or what.

[Sequence]

Something is wrong network wise, are you using Ethernet connection or a wireless connection ? 

[Tannersaurus]

Ethernet