I can relate to this. I don't have a lot of suggestions, myself, since I am trying to work on this too... But I agree, that books on the subject can help somewhat, at least to pinpoint your "core beliefs" about yourself...

The good thing is that you DID have at one time, a good self-esteem, so it IS in there! Oh and that your boyfriend is different than the ex-H. (hopefully in a good way, and if so, I am glad you have that good supportive person for you now.)