Poor connection quality

I’m not a network guy. I just download to play a game in Japan with my wife.
In the first month it was all fun and games (literally) but on the last two weeks my connection is so bad that i’m coming here to figure what is going on. I can’t even watch a youtube video in 144p, my ping on said game was around 300ms wich is normal (im in brazil for now) but lately is about 600~700ms.
Heck, even to load this community forum i need to turn it off.

Anyone can help me, i just want to be able to use it normally like it was on the first days…
(I’m using Windows)

Does it improve if you use anothe rproviders dns?
somethign fast, say ,neustar