How do you get your MMR back to normal?

So mine is below what it should be according to rito. I have won 3 straight, but get less lp every win. How does this make sense? I got 15, then 12, then 11. I mean, I'm not sure how my MMR is so shitty when I'm 50% over the last 20 games to begin with, but that's another story. Am I going to get 8 points the next time I win? I mean, it is like impossible to climb given that I lose 3 games worth of wins in lp.

Tl;dr: Why is my MMR so bad with 50% win over last 20 games, and how do I make it not give me 11 points a win?