I'll let you in on a secret. I used to be just like you, struggling to get attention from women, accept myself, over thinking, whatever. I would still get the compliments (though much less often, I talked to a lot less people and gave off an insecure vibe), but I would think to myself "okay, I have nice eyes but the rest of me sucks." Fortunately I learned a lot, mostly from reading Six Pillars of Self Esteem and A New Earth. Now if I find myself overthinking things or dwelling on something negative, I force myself to think about how much I love myself and all the good qualities that I have. Self esteem and positive self image is like a muscle, you have to exercise it a lot to keep it strong.

Also stand up straight. Its the easiest way to project confidence. Seriously go out one night slouching like normal, make eye contact to see how long girls look at you. The next night go out standing up straight, holding up your rib cage as if you were a valuable and important person. You should notice eye contact lasting a little longer as people are intrigued by what makes this guy (you) so valuable/important (of course, if you have nothing to back this up you're fucked anyways). Also if you're standing up straight you should notice people of either gender giving you a wider physical berth to walk through crowds, you look bigger/more imposing, and they don't want to get pushed around by your broadly held shoulders. Again though, if you're unconfident as hell, people should quickly see through your incongruence and think poorly of you. Personally though, I've found that my mind and body are connected in a 2 way relationship, so that if I force myself to stand up straight I will feel a bit more confident/better about myself. Once you've got good posture down, the next thing to do is to make yourself feel and look comfortable in any situation, i.e., don't be too stiff. To feel comfortable talking to people, practice it. Every single time I am in line at the grocery store or In-n-Out or wherever, I attempt to make conversation with the people around me. If you suck at conversing, I recommend reading How to Win Friends and Influence People.