I think that you expect to get hurt and so you do. Also, in reading your posts I can literally see walls all around you. I don't mean that to sound hurtful at all, just that it's evident to someone looking at it from the outside. I really feel that if you can search out that point where you decided that you were alone or unworthy or whatever the case may be, you can then loose its hold over you and go on to enjoy fulfilling relationships.
And I am a firm believer that every new moment is your prime. You can never pass it! You mentioning that you are well past 25 doesn't change how I see the situation. It just may be a little harder work to untangle the reasons you got to this point, but then the payoff will be even that much greater.
If you can take one thing from me at all, let it be the knowledge that the hard work is worth it.