That's it really. I've pretty much felt this since I was old enough to be sexually/romantically active. Was married for 11 years (still am technically married), not particularly happily, and have had a few other medium-term relationships (1-2 years max) and plenty of flings and dates. But I have never had a relationship where I haven't in some way felt that I wasn't good enough.
I know I'm not conventionally unattractive, scrub up well, I have friends (both the good, long-term variety and plenty of good acquaintances) and without sounding big-headed I know I am good company and a reasonable conversationalist. Am solvent and reasonably intelligent. I know its not especially rational.
But I've always had this deep-seated, fundamental belief that good relationships are not for me in some way, almost like something which was predestined before birth: that I'm not the kind of girl any person would choose as a spouse/long-term partner. And its led me to seek out a lot of damaged and unreliable/unworthy people over the years.
I've had some therapy for it and its helped to some extent in that its allowed me to be able to identify this as something I perceive to be true rather than an objective reality for a long time I actually genuinely believed I was too ugly to date. But it hasn't really shaken that core, instinctive belief that I'm not good enough.
This isn't meant to be a pity party -- I'm genuinely curious as to whether anyone else has felt like this and if they got over it and how?