How do I fix my inconsistent play?

Practice.

It's all about decision making. Your mechanics and positioning will improve, but also work on decision making. If the entire enemy team is at dragon, and you know your team can't win a teamfight on command, try a trade. Take a tower. Steal Baron. Ward their jungle and pick off a random carry who got separated.

so it's hard to fix a problem you dont know you have and from the way you wrote your post it sounds like you dont know where to start. am i correct?>

Well, it happens to me too. First game 16/0/8 300CS next game 0/6/2 70cs.. I think I was too confident the next game and it explained why I was playing poorly. So I just stopped playing and instead watched youtube videos of one of my main VS different matchup and now my games are kinda similar. But sometimes it seems we just have bad games we are not in the mood maybe

Hi hii~ I'd be glad to watch or play with you sometime... then maybe I could answer!

Could be playing characters you don't know very well, could be you tilt too easily, could be that you don't now how to play without a lead(a common problem), could really be a number of things. Generally in solo queue you want to play a character every time if you can, learn how to play almost every matchup. General rule of thumb is have three characters for a role. Your main which you play 90% of the time. Your counter in case it gets picked. And your Secondary in case it gets banned.

Then you just play those three every game and it never becomes a question of character familiarity. Could also be that you get thrown off by your teammates too easily. In which case its a matter of focusing on yourself and not your allies Play the game as you know it should be played. Don't let that vary.