
ANSWER - That's actually quite a complex question because for me although spell work can be of great help in this area, it isn't the first step to improving self esteem. Spell work will enhance the efforts you put in but in something as deeply rooted as your relationship with your own self, you need to put in some mundane groundwork first.
Before answering this I had a chat with another witch who has suffered very similarly and who I've watched spend the last two years on improving her own self image and I asked her what the key steps were that she took. She explained that the first step to liking herself more was to be self honest and understand why she had so little self esteem. She then worked it back as a logical progression to find what fears lay behind it.
The thought process was along the lines of...
Why don't I like myself?
Because I'm ugly -
Why does that bother me?
Because nobody will want to be with me?
Why does that bother me?
Because I'll be alone.
Why does that bother me?
I'm frightened of being lonely.
This might not be the same thought sequence for you but it is a good indicator as to how you can trace back the surface worries to find the hidden fears that are really bothering you. Once you know what they are you can start working on them. Too many people try to treat the symptoms of poor self esteem (for example - I'll lose weight/have surgery/buy expensive clothes - whatever..) but without digging up those hidden fears from their roots you'll always be stuck with them. Work your self esteem back to what is really bothering you and then take practical steps to tackle it. In the case of my friend it was a matter of living her life for her and not being so reliant on the thoughts and opinions of other people. When she stepped beyond allowing other people to validate her life for her and started to validate her own life her opinion of herself rose significantly.
From a personal viewpoint I'd also suggest looking at the bigger picture. When I'm prone to melancholy I like to watch documentaries on space and the universe that show just how insignificant me and my little life are. There's a lot of comfort in understanding your own unimportance and it frees you up to make mistakes without feeling that ever little thing that you do matters. The universe is something like 14 billion years old and you'll live in it maybe 100 of those years. That kind of perspective encourages you to get out there and make the most of it. And if you're not always the prettiest/cleverest/most popular person you know you can be the person who made the most out of their 100 years on earth and that's a hell of a boost for anyone's self esteem.
I'd also advocate slowing down - I find I crash emotionally when I'm working too hard, not spending enough time meditating, neglecting my garden and not enjoying the odd walk in nature. Take some time to shore up your spiritual self. Ignore some of those demands on your time and take some time to let yourself heal gradually. Make the time to sit and listen to whale music on the internet or to take a stroll through the local woods. It's a bit cliched perhaps but if it helps (and it does) - who cares??
In terms of spell work - I did a spell recently to improve a person's self image that may help you. It involves two people but could easily be adapted to one person if you don't have anybody you would feel comfortable doing it with. I held up a mirror and the other person sat in front of the mirror and spoke into it (shades of fairy tales here...)
"Mirror mirror on the wall
Who do I love the most of all?
and then I replied (as the mirror)
"You love yourself the most of all."
We repeated this several (50+) times and I asked the other person to take a non permanent pen and then to write on the mirror with positive thoughts as she felt inspired throughout. At the end of the spell I gave her the mirror and asked her to keep doing the spell every day.
Another spell I've had success with is to take a part of yourself (toe nails..blood..hair) and to place in in a jar with herbs that promote positive thinking (St John's Wort...Lavender..Chamomile)
Seal your essence up in the jar tightly and visualise it as the peaceful part of you that nothing can attack.. Seal the jar with candle wax and then shake gently to activate when you are feeling at a low ebb.
Good luck with it, I very much hope you start to feel better soon.
Image http://www.deviantart.com/art/Mirror-Mirror-271847507