Since I can't link guides I haven't created myself in my own guide section on my profile (and didn't want to waste a whole box on "my favorite guide"), I decided to create this little reference here instead.

There is basically one thing you need to know in order to understand why you haven't ranked up lately even though you are on a winning streak:

The chance of how likely your rank is to change (up and down) depends on your frequency of games. The more often you play, the more stable your rank becomes and thus is less likely to change when you win or lose.

If you want to learn all about this so-called ratings deviation (a pool of points that inreases the longer you haven't played and decreases the more frequently you play), as well as other basics about CS:GO's ranking system, please check out this guide.

It's the most accurate out there:
http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=492394779
Cheers!