Internet keeps disconnecting itself

Hey guys, I am really desperate, I am trying for days to solve this problem so I hope you have some ideas.

I installed Windows 7 via Boot Camp on my 2012 Macbook last week to use some programs that are not available to OSX.
Installation went through easily and I installed the drivers on the USB Apple makes you download.

So far, so good.

After activating the internet, I start to notice that the connection keeps switching between extremely fast and extremely slow. Mostly slow, though. And then websites suddenly stop to load. I am still shown full bars of connectivity. Then, after 30 seconds or so, a yellow triangle with a black exclamation mark is shown over the connectivity bars and it says no internet access. After a minute or so, this disappears again and internet starting to behave normal again for another minute. Then the whole cycle repeats itself. I installed all the drivers for my router manually, so it cannot have to do anything with the drivers.

All other devices work perfectly fine with the wi-fi, and even on my macbook when I switch to OSX there are no problems whatsoever.

Please help me guys.