MMR

I started climbing from bronze 3 , i'm currently bronze 1 , meaning I've won more games than I've lost .. I have a 60% WR on twitch and khazix , but My MMR is still somehow getting fucked ? I uses to win 24/23 and lose 14/15 , now that I'm bronze 1 close to promos , I lose 18 LP and win around 22/20.. Why is that ? Anyone can explain to me ?