Realize that it is possible to overcome your low self esteem and lack of self confidence! Many have done so already.
Low Self Esteem (LSE) is complex and deep, it has many layers and aspects to it. Anticipate that it is going to take time to overcome it. It's a long term goal and will take at least a year to accomplish.
First, raise your awareness on how it runs in your life - the thoughts, feelings and behaviors that are caused because of it. To do this, you'll need to study it. For a start, read Breaking the Chain of Low Self Esteem by Marilyn Sorensen and The Six PIllars of Self Esteem by Nathaniel Branden. These are a must read - mandatory! No excuses.
Learn about and use NLP techniques. These work amazingly well for such emotional issues.
Learn how to effectively overcome limiting beliefs. At it's core, your low self esteem is caused by a deep seated belief in your unconscious that there is something wrong with you, that you are deficient, that you are inadequate. This is the mother of all your limiting beliefs. You also probably have other beliefs such as "I'm not good enough", "What makes me good enough is other people thinking well of me", What makes me good enough is being perfect", "I'm incapable", "I'm incompetent" and so on. You must learn how to effectively challenge all of these beliefs so that they crumble and break down. You challenge them by challenging their validity. Ask questions such as:
Where did this belief come from?
Holding this belief helps me feel protected from harm, like a baby blanket, in the following
way...
How is this belief only a partial perspective on the world?
An alternative – equally valid – interpretation of the facts that caused me to adopt this belief is...
How is this belief flat out false?
What would an impartial 3rd party say about my holding this belief?
Three counter-examples to this belief are...
An alternative belief that might be even more accurate is...
(I'd like to credit the above questions to Leo Gura). Challenging your beliefs in this way will either release them entirely, or replace them with a more accurate and empowering belief. First, identify and gain awareness on your limiting beliefs. Then, challenge them until they break down.
Reprogram your unconscious mind. Get 15 cards. On each one of them, write a positive trait that you have. It could be a small phrase, maybe a long sentence or short paragraph. If you have difficulty coming up with them, ask your friends and family. Then, read each one every morning for the next 90 days consecutively - this is very important! Anticipate that this will not be easy. The first week will be easy. The second week will get a bit harder. The second month will be much harder. Your mind will tell you that you've already memorized all of them and so what's the point. To program your unconscious mind, you need a period of 90 days. And you cannot miss a single day in between. Discipline your mind to do it every single day for 90 days, no excuses!
Stay strong.
I wish you the best.
