Well, at least you're honest chaser, which is more than many, and there probably is no magic formula for changing years of ingrained habits.
But sometimes I wonder are people really being fake, are they really only acting like being friends, or are they really trying to be friends and its only your interpretation that they are being fake. Many times ones perception of peoples motives and actions are not what the person intended -- I know I've done that more than once.
I'm not saying everyone is genuine, but maybe give them some slack, and look at it from their perspective, and try not to base it on body image. That doesn't mean that everyone will like your, or you can expect the world from everyone. Just that maybe they aren't treating you as lowly as you treat yourself. Also you seem to tie your emotional well being to that of others, or at least how you perceive others perceive you, and that's a guarantee for an emotional roller coaster.
It isn't easy, and if you don't have it already get some professional help, and certainly all of us here at RJ can listen and give advie, but that's limited, and you probably need someone who can work one on one with you.