That ranked Grind

So I recently realized that something is messed up with my MMR. Last I heard if you have a 55% win ratio you should climb. Highest I've ever been is Silver 1 but for some reason, when I win games I get 20-21 lp, and when I lose I lose 17-20 lp... My last 20 games are def more than 55% wins so its kinda rough that Im sitting on 6 lp cause losing a game completely undoes the win I had before. Someone have any way of fixing this?