Hey lovenature,
Yes, I can certainly relate to what you describe. Definitely. I think it's almost always about not feeling good enough in some way that allows us to stay in situations that are not good for us.
During one of our first blow-ups my ex called me "a bully who always has to have her way". It was crudely put, and not really fair at all, but something about it resonated. I can be quite willful and determined, that is true. He also said things about how I kept myself distant somehow and asked too many probing questions that always seemed to put the focus back on him. Also true.
I had heard versions of that before in other relationships and I took it to heart and eventually, after permitting many disrespectful and unloving acts from him, decided to mend my ways. I remember thinking I had "met my match", someone who was not above being as callous as I could apparently be. My previous partners had always been kinder and more circumspect in how they criticized me, but this one pulled no punches.
It was very wounding and disorienting and absolutely made me question everything about myself and the kind of person I thought I was.
I realised, after about 6 months of reading these boards, and some of the suggested books and articles, that whatever issues I had were not going to be fixed by staying in contact with this person. I thought, read, cried, talked to friends, let myself really look at what parts of myself I deeply thought were "not good enough" and tried to see that from other perspectives. To look at some things I had to do cognitive wrestling with myself, or re-framing as the literature usually puts it. For some others, I just tried to love, the way I would a child who was crying. Do you know what I mean? The support and engagement of the community here has been invaluable. I am still walking with all that, no quick fix for this, but my shuffle is more of a stride now, most of the time
Working out, as I recently did here in another thread, what my top ten values were was also really helpful.
You say you sometimes feel better and then worse again, you also mention depression. I'm sorry, I've not had time to read your previous posts, so maybe you've already spoken about this; but if you are depressed, have you the support of a therapist?
And what exactly do you mean by feeling "worthless"? In a general sort of way about everything? What do you do in your life that helps you to see yourself as competent, good, loving, whatever it is that you are lacking?