How can I build confidence?

Get into therapy to find out why all the self hatred.
Everyone can benefit from some professional guidance at least once in their life.
You need to learn to change your thinking, get out of the loop of negative self loathing.
Our thoughts do create our reality, you are what you think as much as you are what you eat.

The more you focus on your flaws the more you hate yourself, and the more you focus on your strengths the more confident you become.
You seriously need psychological intervention and a bunch of strangers on the internet cannot help you other than to advise you to seek counseling.

Do you belong to any groups? Do you enjoy any particular activities? These types of gatherings generally make a person feel as though they belong somewhere. Plus share a common interest. Shared interests and similar goals do build confidence in oneself.

Physical beauty is often subjective, but internal beauty is universal.

All my life I thought I was ugly. I realized that no woman was going to be interested in me because of my looks, so I had to do other things to compensate. Some of them were on purpose, and others were kind of accidental.

I knew women like guys to listen to them, so I practiced listening. I didn’t know that women admired intelligence, but I managed to develop some intelligence. Or maybe I was born with it. In any case, I loved learning and I got as much education as I could.

Later on in life, I got some therapy. Eventually I learned some mental techniques to help me cope with my negative self view. In my case, I learned I can’t fight it. I can’t make myself stop those thoughts. But what I can do is learn how not to be attached to those ideas. I learn to recognize the thoughts that are not helpful, and to not let myself think or obsess about them. Instead, I let them go. I turn to other thoughts, and soon the thoughts that hurt me are gone.

It’s a form of mindfulness, and you can learn it in mindfulness classes or in yoga or meditation classes.

It sounds like you need more experience and maybe some therapy.

My experience is this (and I’m not lying): I have met very attractive people that become ugly to me once I get to know their awful personality. Conversely, I have met average looking people who become beautiful because of their kind and brilliant personalities. It really isn’t about what you have; it’s about what you do with it.

It is fairly normal to question many things about yourself when you’re a teen. Try to aim your life in the direction you want to go. Educate yourself on a variety of topics and become a good conversationalist. Learn to ask good questions to draw people out. You’ll have missed starts at first. Learn from them and keep trying. Work on humour. Being funny can be an ice breaker in so many situations. Think of yourself as a work in progress and, maybe most of all, BE KIND TO YOURSELF!

As soon as you start experiencing positive outcomes on a regular basis your confidence should get better and better.

I’m struggling with this now. One of the most important things I’ve learned thus far is that you have to change your inner dialog. I believe it’s one of the cornerstones that so much is built upon. You stated “I tell myself the beauty is a lie.” You need to develop a zero tolerance for the negative statements that run through your mind. I think if we can master this first a lot of other aspects will fall into place.

Read this poem until you believe it…

Our Greatest Fear
It is our light not our darkness that most frightens us
Our deepest fear is not that we are inadequate.
Our deepest fear is that we are powerful beyond measure.
It is our light not our darkness that most frightens us.
We ask ourselves, who am I to be brilliant, gorgeous,
talented and fabulous?

Actually, who are you not to be?
You are a child of God.
Your playing small does not serve the world.
There’s nothing enlightened about shrinking so that other
people won’t feel insecure around you.

We were born to make manifest the glory of
God that is within us.

It’s not just in some of us; it’s in everyone.
And as we let our own light shine,
we unconsciously give other people
permission to do the same.

As we are liberated from our own fear,
Our presence automatically liberates others.
~Marianne Williamson

I agree with @Ela on the Quote.

I had it framed on the wall and read it every morning during a past difficult point.

Additionally, move away from negative energy and try to surround yourself with positive people.