Well, Gery, at the risk of just sounding like I'm going into further psychobabble, here's the next shot. You just said above that you've been sexually active since you were eight years old. If that's true, then you were the victim of sexual abuse, even if it was with someone of the same age (which is referred to as child-on-child abuse). Sexual abuse at such at early age often plays out in a variety of ways, including seeking partners where
sex is the only connection
the victim is drawn to pleasure others, but receives no satisfaction
shame, guilt, or disgust in one's self is the outcome
promiscuous behavior is exhibited or avoidance of sex occurs
fear of or lack of belief that true intimacy can be achieved occurs
and, among others, weight is gained as a way of creating
a barrier of "unattractiveness" so that others will keep their
distance, even while desiring intimacy.
I've worked with a number of young people over the years who have experienced sexual abuse, and many of them have exhibited some or all of the characteristics listed above. Even if they do not see the initial abuse as something terrible, they subconsciously are still driven to act out the list above. I'm not saying anything you've described is definitely linked to your early sexualization, but it's as possible a theory as any.
So the possible progression here? You experienced sexual contact at too early an age, subconsciously beginning a desire to seek out unsatisfying sexual experiences. You had an active sexual life as you got older, but it left you unfulfilled, and often full of shame, guilt or fear. As you became more disenchanted by the whole situation, you internalized those emotions even more, deciding that it must be you that is broken, ugly or repulsive in some way, so you started putting on weight. The weight became a good thing to blame, along with age or lack of funds, for why no one would want you, and then placing yourself in situations where that proved to be true became the norm.
I don't know if this is what is playing out here. I know that when someone offers you a perspective, you have this way of dismissing their points without really disproving them, sort of a "ding, thanks for playing, that's not it" way of dealing with it. As one of the posters above pointed out, there are far meaner, uglier, fatter, older, poorer, less interesting, less intelligent, less humorous men than you who are getting laid--and many of them are in actual intimate and caring relationships while doing so. So if you're looking for reinforcement in the idea that there's ultimately just something so wrong with you that you can't find someone, well, I guess I can't offer you that.
But I will offer this

, even if you shoot down everything I've just said.