You can add the fact that you have literary talent to your long list of other fine qualities. I love the fruit fly metaphor! You asked me several questions. The first being, 'Why does a woman with low self-esteem pick a man who needs fixing?' You said yourself that you don't feel worthy of a good partner (who would want you?). The best you think that you can do is find someone so defective that he needs you for his survival. Plus, he is less likely to leave you for someone else or someone better.
When you choose someone who needs fixing, there is the mistaken notion that being needed with boost your self-esteem. Unfortunately, caretaking leaves you feeling used up and even worse about herself. The Miss Fix It role actually diminishes your self-esteem over time. Caretaking (trying to fix others) is a guaranteed path to low self-esteem. Since you can't change others, you are doomed to fail. Plus, all the energy spent on giving to the other person leaves you feeling empty and depleted, which is sure to make your self-esteem dip even farther.
In your later questions you ask, 'Do I really have to love myself before I can love anyone else? Do I have to love all of me fully before I can love another?' And'Is it wrong to think that a good, healthy relationship can help me to be a better, more attractive, stronger person?' It is true that no lover is going to be able to heal your wounds or improve your self-esteem. Yes, you might feel temporarily boosted by snagging a great catch, but unless you identify the root cause of your low self-esteem and resolve it, your low self-esteem will always resurface.
So, let's try to figure out where your problem stems from. I am going to lay out the most likely possibilities. You can identify which one(s) fit. Choosing damaged partners and then trying to 'fix' them can be an unconscious attempt to fix a parent who was damaged. Since all children are omnipotent (think that they have the power to change the world), it is normal for mistreated or neglected children to think that they have the power to fix their parents so that they can finally love them properly. Perhaps you still live under the illusion that you can fix your partners (just like you believed that you could fix your parents). When you fail in your attempts, you naturally hold yourself responsible for the failure. The sense of failure diminishes your self-esteem.
See my Advice Archives under repetition compulsion and unfinished business to see if you are recreating childhood relationships in an effort to fix one or both of your parents. Low self-esteem can also be the result of misdirected rage, a pattern that begins in childhood. In a nutshell, all children naturally swallow their anger toward their parents. This is because young children don't see a difference between thoughts, feelings, and actions. If a child is angry and wishes a parent dead, the child thinks that his/her thoughts are powerful enough to create death (again the omnipotence of childhood). Since the child needs his/her parent for survival, he/she cannot permit such thoughts and feelings to continue. The feelings get buried, but they don't disappear. They fester inside the psyche and resurface in various ways: physical ailments, headaches, digestive problems, self-destructive thoughts (cruel self-talk in which the self is put down, leading to low self-esteem), self-destructive actions (food, drug, alcohol addictions, gambling, excess spending, wreckless sexual activity, etc. ), depression, anxiety and many other possible symptoms. If you read your letter to me, you will see that it reads as though you are engaged in self-punishment. You say that you can't allow yourself to believe that you deserve a good a partner. You sound like you aren't entitled to happiness, success, etc. .
In fact, it sounds like you are actually living a life sentence, doing penance for a crime that your unconscious knows you committed. The unconscious always arranges to punish the self for buried anger. It's strange how this works. Once the anger is owned and brought to the light of day, this kind of self-blame and punishment often fades away. Another cause of low self-esteem is childhood abuse. If you were verbally or physically abused, you will not only have thought that you deserved the mistreatment (to protect your parents from your anger toward them you would have blamed yourself). Such experiences will have taught you that being put down is normal and that this is how you should be treated. In no time you would have learned to mistreat yourself the way you were mistreated. It is also possible that you identified with a parent who had low self-esteem.
As you may already know, the self is formed by unconsciously absorbing all aspects of your parents. We absorb into our selves our parents thoughts, feelings, attitudes, values, behaviors, as well as whatever feelings our parents have about themselves. If a parent has a low self-esteem, it is common for the child to put him or herself down. If this possibility fits, you are going to need to consciously separate yourself from the parent who had low self-esteem. Putting oneself down can also be an unconscious way of punishing one's parents. People who have been mistreated in childhood live with a tremendous amount of anger that was never communicated. One way that the unconscious communicates that anger is by arranging for you to suffer and fail. Each time you do, the unconscious symbolically points the finger at your parents and says, 'Look how you ruined my life. ' Each failure is designed to release anger at the people who created you. While anger is released, the person who vents in this way is actually ruining his own life, punishing him/herself as he digs the knife in his parents. Keep in mind that this mechanism is usually unconscious, meaning that the person who puts himself down, suffers and/or fails as a way of venting anger toward his/her parents isn't aware that he/she is doing it. You would be wise to examine whether your attempts to caretake are really a misdirected effort at fixing yourself.
Many caretakers are notorious for giving to others the love and support that they need. The fantasy being that if you fix your parnter and fill his tank, he will then be able to give back to you, thereby filling your empty tank. Can you see how this plan leaves you dependent on another person for your salvation? If you succeed in fixing the guy (and he is able to love you), then you can finally feel all right about yourself. If, however, you can't fix him, you feel like a failure, your self-esteem drops another notch, and you are still left starving for the love you always needed. In the end, your only way out of this bind is for you to heal your wounds.
You need to become your own mother, caretaker, fixer upper, whatever you want to call it. You must consciously put yourself first and give yourself the emotional nourishment and support that you needed from your parents. Treat yourself the way you wanted your parents to treat you. As you begin to heal the child inside of you, magical things will happen, most important of which is the fact that you will no longer need to choose broken men to fix. You will feel whole and worthy of love and then and only then will the right partner come along.