always trying to fight a teamfigh
Theres your problem.
First of all, you arent CSing ok if you finish a game with 150 CS.
Perfect CS at 10 minutes is roughly 108 (a little more for midlane). So if youre FINISHING a game at that number, you arent even laning properly, let alone CSing well.
You CS every time you can. 10 creeps = a kill. Kills are worthless unless you gain something from them (denying xp, getting tower/objectives, roam etc.) so stop trying to force fights.
There is also no reason to be grouping at every moment. Far too often in games people will group randomly mid for no reason. There is no creep way to push with, no tower to take, no dragon to threaten. You don't need to be there, ignoring those juicy side lane waves building up. Thats massive CS going to waste.