Hmm, I agree, it makes me feel conflicted as well. I think at the root of your problems lies not your appearance, but your impulses/conscious decisions that make you choose whom to date, and your perception of reality at the beginning of relationships.

Many assholes are quite smooth and might give you attention, make you feel good about yourself, and if you have insecurity that is obvious, exploit it to get you hooked. You should evaluate sincerity of the attention you get when you just start seeing someone. Does the dude's attention feel hollow? Composed of sweet nothings? Is he really looking for a real relationship, or just any relationship? If you are just anyone, convenience that meets the need, so to speak, assholes will move along when better offer comes along.

Do you want a real relationship? Do you offer hollow sweet nothings to your boyfriends, and even if they want a real relationship, seeing that you offer only hollow place-holder, they move along to better offers? (probably subconscious decisions).

Deliberate on your past relationships. Do not try to find whose fault was what, but what was the truth of the failing? If you find faults within, fix them. Best of luck.

Source: had tons of asshole friends, who did exactly that. Girlfriends they had, but were ready to jump to better ships the moment it became a possibility. The hollowness of their relationship was immediately visible right at the beginning, because there were no real feelings there, only surface play acting. I still don't understand why those girls fell for such cheap methods. Probably because brain kinda stops working properly when met with objects that attract them, make them feel strong emotions and so on.