Stuck and need opinions

Hey guys so this is my second season of ranked play. Last season I was placed b5 and worked my way up to s3. I thought I was learning the game and improving but this season has seemed to prove otherwise. I was placed b4 and climbed extremely quickly to b2 and ever since it is one never ending loop of getting all the way to series for silver and falling right back down. I have played a lot of champions in ranked mainly due to experimenting in ranked 3s. When it comes to ranked solo I shoot for mid. That is where I am most comfortable and where I enjoy playing the most. I can play any role if need be. When playing mid I tend to migrate to the same pool of 5 or so champions: ahri, lux, yasuo, zed, orianna. Based on my stats am I playing these characters badly? Am I not farming well, too many deaths, what do you see? It seems as if I have hit a brick wall and can't get past it which is weird to me seeing as I seemed to improve so much last season. Now I can't even get back to where I ended and I don't know why.