I don’t know how your low opinion of yourself got started but it certainly has taken on a life of its own. You are ruminating. That means that you are going over and over and over and over how inadequate you are. Like water moving over a stone, the repetition is wearing you down and out. By repeatedly telling yourself what a worthless person you are, you are reinforcing your sense of your own worthlessness.
Enough. You don’t have to do that. Since you do know that things you do are “stupid and mean,” you aren’t psychotic. You do know that you are stuck in negativity and you do know the difference between right and wrong. The fact you are ignoring is that you are choosing the life you have. Because it is a choice, you can choose a different path.
Since you haven’t been able to pull yourself out of this hole on your own, I hope you will make an appointment with a therapist. Therapy will help you stop the ruminating and start to put a better life in motion. Cognitive-Behavior Therapy would probably be the most helpful.
Writing to us here at PsychCentral was a very good start. It shows that you haven’t really given up on yourself. Take that little indication of self-respect another step. Get yourself the help you need and, yes, deserve.
I wish you well.