Hi, I'd like to help you with your question.
I agree with you, it is likely that your feelings are more deep seated. Being told to get lost as a child is hurtful and can cause a child to feel unwanted and rejected. As an adult, you would have trouble feeling wanted in any social situation including romantic relationships. You would always feel like you are lower than others and do not deserve to be treated with respect.
It is good that you have tried working on this issue. It shows you are motivated and that is half the battle in feeling better and overcoming a problem like this. There are other things you can try as well.
One, therapy is a good option in finding the root problem and helping you build your self esteem. To find a therapist, ask your doctor for a referral. Or you can search on line at http://www.goodtherapy.com.au/find_a_therapist.php or http://www.findatherapist.com.au/.
Two, you can educate yourself regarding self esteem issues and learn how to work on this issue yourself. There are many resources out there to help you. Here are some to get you started:
Self-Esteem: A Proven Program of Cognitive Techniques for Assessing, Improving, and Maintaining Your Self-Esteem by Matthew McKay and Patrick Fanning
The Self-Esteem Workbook by Glenn R. Schiraldi
Healing Your Emotional Self: A Powerful Program to Help You Raise Your Self-Esteem, Quiet Your Inner Critic, and Overcome Your Shame by Beverly Engel
You can find these books on Amazon.com or your local library may have them for you.
Some other techniques you can use:
Learn to pinpoint your thoughts and beliefs about yourself- in other words, what does your self talk sound like? Are you telling yourself you are not worthy, and are you repeating what you heard as a child?
Be aware of how you are reacting to your thought process- are you feeling upset, sad, angry or depressed as a result?
Challenge your negative thinking- for example, if you are faced with a room full of people and you notice you are thinking that you are less important than they are, try asking yourself why. What makes you less than they are? What makes them more important? Is it because you say so or you were told that as a child? Projecting your beliefs onto the people in the room makes it hard for you to face anyone. The trick is to stop telling yourself you are less worthy and start seeing yourself as equal and deserving.
Also, challenge what your family told you as a child- in your mind, reset the circumstances of your childhood. Picture yourself as an adult watching your brothers tell you as a child to get lost. What would you, as an adult in that scenario, say to yourself as a child? How would you respond to her?
These techniques can help you begin to explore the roots of your feelings and help you gain the power to overcome them.
I hope this has helped,