I never realized that I was that much of a dick.
How could you not realize that you are coming across as a dick to people?
I don't understand what I do that makes people think I'm a dick
There is no valid reason to be a dick to people when it is just as easy to be nice. You need to improve your behavior towards others or you will suffer a bad reputation as a result.
That's just your opinion. I'm not a dick. I'm honest. No one is a dick to me.
Well if other people feel you are a dick and you do as well, odds are you may come across like that. A little effort to be nicer may make it much easier for you to find new friends. Also, this may improve other's lives since you will be kinder to them.