My answer is: try everything. That's why I wrote it will require time and dedication.
I literally used every technique I could find on the internet. NLP, visualisation, affirmations, self-hypnosis, writing goals, reading, writing journals, you name it, I tried it.
Don't push yourself out there for now. Start educating yourself about your problem. You may want to change your self-image first. I suggest you read Psycho-Cybernetics:
Amazon.com: Psycho-Cybernetics, A New Way to Get More Living Out of Life: Books: F.I.C.S. Maxwell Maltz.
It's a book written by a surgeon which discovered that the problem of his patients was not that they were ugly but because they THOUGHT they were ugly.