i think you're suffering from analysis paralysis. in other words, you're thinking much too deeply about the potential consequences of your actions. and this is causing you to either recall or simply imagine what are completely worst case scenarios. remember the dr pepper ad: "what's the worst that could happen?". well life generally isn't like that at all.
my advice is try to ignore your fears and take up the opportunities that come your way. otherwise you're denying yourself the very experiences that will help you to develop the social skils that you need to cope better with you life.
i hope that helps. it's always easier to give advice than take it. but trust me on this. everything gets better with practice.
the is a book entitled 'feel the fear and do it anyway'. not one i rate very highly but i think the title is a good one to remember, provided it isn't applied to wrestling with crocodiles and alike!