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.

[Psyrus]

What troubleshooting besides speedtests have you conducted thus far?

[NO FUN ALLOWED]

Basically just taking the ethernet out and putting it back in, uninstalling the drivers and reinstalling, restarted modem, called cable company. Cable company of course says it's not them, but I mean it shouldn't be them because on my old computer I never had this problem.

[LITOralis.nMd]

give us the exact parts, manufacturer and model numbers.
BE SPECIFIC!

see, I'm guessing you have a Asus MoBo and installed the Asus Network iControl utility.

but since you didn't give us any useful information, it's a total fucking random guess.

[Psyrus]

give us the exact parts, manufacturer and model numbers.
BE SPECIFIC!

see, I'm guessing you have a Asus MoBo and installed the Asus Network iControl utility.

but since you didn't give us any useful information, it's a total fucking random guess.

I don't think LITOralis meant to be as harsh as his tone suggests, but there are a lot of support queries lately and it can wear on a man's sanity... I've certainly been guilty of similar in the past. But yeah, please do provide some hardware/configuration information, as much as possible

Also, if you have a laptop or anything, can you check if it exhibits the same behavior?

[NO FUN ALLOWED]

No laptop but my phone behaves normally through wifi, my mobo is the gigabyte z87x-d3h ultra durable 5 plus, is that all you need in terms of hardware specs? I gave my internet speeds in the OP.

[LITOralis.nMd]

we need all your specs,
motherboard,
firmware,

CPU,
OC or not?

ethernet drivers,
wired or wireless connection,
IP4 or IP6
router make and model, firmware revision,

Your ISP might be throttling your connection,

You might be overloading your HDD's write speed,

You might have conflicting firewalls and antivirus

You might have incorrect options set in your ethernet connection

Have you performed a full set of speed/jitter/reliability/sustained d.l. rate/ tests yet?

try this at 200MB on custom settings:
TestMy.net Download Speed Test

sustained test:
Las Vegas Data Transfer Test

a lot of testing services:
Speed Test : upload and download | DSLReports, ISP Information