emi,
I know it is not easy to change the way you think about yourself, but with time it can happen! It has to begin with you seeing yourself as others see you. Why not get them to write down all the great things they think about you and then read this when you need that all important self-esteem boost.
I know having my Master tell me everyday that I am a beautiful, sexy woman has made me believe it, even though I did not think this way a year ago!
Good luck and take things one day , one moment at a time.