Its really a perspective thing. You are of course going to remember the good you do more than the bad you do and the bad your team mates do more than the good your team mates do - this is just human nature. I'm going to point out your good with your bad so that you see that I am not just trying to attack you. I see potential in you and think you can grow.
You have had games in your last 20 where you did bad such as:
7-9-8 in a winning game
9-9-3 in a losing game
3-6-2 in a losing game
9-11-10 in a winning game
5-12-6 in a losing game
1-3-1 in a losing game
1-7-3 in a losing game
2-8-5 in a losing game
But you also had games in your last 20 where you did good:
8-4-1 in a losing game
15-5-9 in a winning game
23-9-8 in a losing game
13-0-8 in a winning game
15-10-14 in a losing game
7-7-16 in a winning game
7-1-9 in a winning game
13-3-9 in a winning game
7-4-10 in a winning game
So you had 9 good games and 8 bad games. One of the good games was only a half point, so I'd say it was about 8.5-8. In your bad games you won 2 of them when you should have lost. In your good games you lost 3 that you should have won. Considering you are within half a point between games you did good and games you did bad and within a point of games you should have won and lost and vice versa I'd say you are in a pretty even spot.
Don't focus on your team mates as much and just focus on improving yourself. Focusing on your team mates will drive you crazy. Learn how to set game play goals for yourself and concentrate on hitting them. Setting game play goals will take your mind off your team and give you a tool to use in game to measure if you are having a good or bad game. Some goals I set are X level by Y minute, X build by Y minute, and X towers by Y minute. These goals also make it easier to tell if you are ahead enough to try to help your team or if you can't afford to fall any further behind by making risky plays.