Self esteem issues can originate in many ways. But the most common ways are past abuse or neglect
either by parents, caregivers or other significant others in your life as a child. Or you may develop low self esteem if you suffer through a trauma or significant issue such as a job loss or divorce. Not getting your needs met as a child is a common reason behind negative thoughts and low self esteem. Children learn that they receive validation through their relationship with their parents or caregiver. But if that relationship is affected by poor parenting or absence of a parent, the child will have trouble getting those emotional needs met. And as children do, they look to themselves as the reason why their needs were not met, usually feeling they are somehow defective.
By identifying the source of your low self esteem, you can pinpoint how to combat it. Trying therapy, including techniques like Cognitive Behavioral therapy and educating yourself about your issues are very good ways to address how you feel. Educating yourself is one of the best ways to work through a problem like low self esteem.
You may also want to consider therapy. By talking to someone about how you feel, you can increase the chances of addressing your issues. This is because a therapist can offer insight that you may not be able to see for yourself. And sometimes just the act of talking out how you feel can alleviate some of the burden and make your thoughts clearer and easier to understand.
To find a therapist, try asking your doctor for a referral.
Changing your thinking patterns also can help. Start writing down how you think about who you are. What kinds of thoughts do you have about yourself and why? Then change any negative thoughts by practicing saying "stop, that is not true" and replacing the thought with something more positive. You may also find that most of your negative thoughts are not based in fact but are formed from past messages you got from others. Try writing down all of your good and positive traits. And focus on those when you feel down or bad about who you are.
You can also read more about self esteem issues to help you learn ways to address how you feel through self help, which is also very effective. Here are some resources to help:http://psychcentral.com/lib/2011/self-esteem-struggles-and-strategies-that-can-help/http://www.newharbinger.com/PsychSolve/SelfEsteem/tabid/159/Default.aspx
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
How to Raise Your Self-Esteem: The Proven Action-Oriented Approach to Greater Self-Respect and Self-Confidence by Nathaniel Branden