Brand new computer, bad networking problems

[NO FUN ALLOWED]

So I recently built my first computer, everything went really smoothly, it started up the first time and everything. BUT my 30 down internet connection instantly turns to like 3 down (or less) once I download a game or something of that size. Also a few times now I've been playing CSGO and have had TS3 open and both seem to lose connection but I can still browse the web fine. I've installed my mobo drivers which included LAN drivers for the Ethernet. When I speed test with nothing running I get my usual speed, 30~up, 4~down.