Do not be worried. It's impossible to be perfect, we're humans and all of us make mistakes. I used to have same kind of thoughts you have now, so I tried to be a better Christian. It didn't work out. After some time I understood that the change cannot come from me, it comes from God. Don't try to change who you are, instead open your heart and trust God. Pray and give your life in his hands. You should experience changes in your mindset, because you no longer demand so much from yourself.
Also, I'm sorry to hear you had problems with your church. Same happened to me. I don't attend church right now, but I am still a Christian. It's lonely and difficult sometimes, but if you just trust God with all your heart you can manage. He doesn't abandon anyone, not even those who are isolated and alone.
