I win 10 games and i didn't get any key fragments :( pls explain

You can get a key fragment randomly when winning a game, with a higher chance when you're in a premade party. You probably just got really unlucky in those 10 games.

Also the more key fragments you have gotten, the rarer they are. It seems that they get exponentially rare after you get 3 key fragments in a month. I got 3 key fragments easy this month. After that, I have not gotten any more keys. I was getting them like 1 every 3 wins. I've gone 7 wins now or so without a key fragment. It seems that getting 1 key a month will be easy for those casual players. After that, you're going to have to farm them out hard core so hopefully you have a ton of spare time to commit.