I suspect you've already taken the first step by realizing that the things you experienced when you were younger have scarred you, both emotionally and spiritually. Perhaps your letter will encourage parents not only to love their children, but also to let them know they do.
No, I'm not a psychiatrist, but if you think it might be helpful to discuss your problems with a skilled professional counselor, I certainly would encourage it. (Your pastor may be able to suggest someone in your community.) One of the spiritual gifts God has given to some individuals is the gift of wisdom (see Daniel 2:21).
However, the first step I urge you to take is to turn to God and discover how much He loves you. Your parents failed you; what they did was wrong, and your mistrust and feelings of unworthiness are understandable. But God will never fail you, and His love for you will never fade. Once you realize this, your life will never be the same. The Bible's words are true: "If God is for us, who can be against us?" (Romans 8:31).
How do I know God loves you? I know it because He sent His only Son into the world to give His life for you. God loves you that much! Ask Christ to come into your life today, and then ask Him to guide you to a church where you can grow closer to God -- and closer to others.