I think I am a bad person and I have issues.
Why do you think you're a bad person and what issues do you have?
I think I am really selfish to be honest.
It is good to do self reflection on your character. It is not always right to be selfish and it is good to work on this.
I've done a lot of thinking and I think I need to become a better person and change my life.
You are thinking absolutely right. You should read self-help book, they're pretty useful.