Thank you for being so honest. This the first question I read on Freelancing, after answering many questions on StackOverflow. It is refreshing to read this. I personally do not believe you need "help" to do anything you want to do. Maybe some books... but you have an amazing advantage I mention below.
My local veterinary clinic has a young man in it who sounds how you describe your self. I find that the effort he puts into every interaction makes me value his strength, and each time I see him, he is stronger and brighter and it seems easier for him. I look forward to our awkward moments and he seems to feel the same. Life is a puzzle being fit together, it's not anywhere near comfortable to be alive. So remember, you are totally normal to be anxious, no matter how it feels like that is inappropriate. It is just feeling more of the truth of life than most. Anyway...
Why is my ultra-shy & 'awkward' local veterinary clerk changing so fast?
I feel it is because of the "animals," far more than the "humans." In your case, you have such a huge gift ahead of you. The animals literally give you their love and self-respect. They fill you with everything you said you don't have. That's what they do to us. We give them order, they give us love. So just like how in massage the goal is to "feel the bones" not "kneed the muscles" ... focus on the animals, and ask for what you're worth. Charge no less than 20% below the market rate, even at first.
If you do, you respect your self, the animals, and you will attract the kinds of clients who have the energy inside to see you for who you are, and appreciate you for who you are for their animals and their own lives. You are a very sincere person with hope and faith in your self. Congratulations! You are an asset of amazing value to anyone and everyone you force your smile upon. If it feels like force, it's really not. It's making your smile. We all were pushed out of another body, we were all the cause of tremendous pain, just to walk the Earth... so too our smiles.
One day, you'll wag your tail by accident and smile at moments of inner turmoil. You are doing the right thing to push into the unknown and uncomfortable. Keep going. Charge what it costs you to breathe.
One suggestion only... go sit at a dog park with your dog, even if you need to borrow one... and just play with whoever your dog finds for you. The animals are more of a factor than we perceive them to be. Don't think about the humans so much, don't try to appeal to the humans... just be your dog's friend, and have some business cards ready. Don't focus on anything but what the animals need and appreciate. The humans will not only deal with it, they will admire it... or you don't need them as clients.