I can identify with the OP very much. I've felt for years, before I ever understood that STBXAH was an addict, before I had any clue about codependency, that I did not have much of a sense of self. It was very obvious to me that there was something lacking. I felt very envious of people who exuded self-assuredness, who knew who they were and what they wanted.
4 years ago I started seeing a therapist, and he helped me through some very difficult times, times when survival was the main goal. We were able to peel back a few layers during that time, but it was very slow going. Now that I'm out of crisis (but still in limbo), I can really get to working on ME.
I am taking this time, as long as I need, to be deliberately single because this is the first time in my entire life that I've had the opportunity to figure all this out, and I want to heal my life more than anything in the world.
I hear you on the Meyers-Briggs thing. I don't know how to answer a lot of the questions. I DO know that I'm very much introverted, and I think that I'm a feeler, but the other two are still somewhat of a mystery to me.