Hmm..fret not, you're still only 18. 
Regarding your fear of rejection, while understandable, it's
ultimately a matter of knowing when and how to strike the right
balance I guess. It's like a gamble and ultimately, you've to
decide whether the rewards are worth the gamble. Think about it :
would it not be better for you to find the right guy(even after a
couple of rejections if need be) by being a little thick-skinned
than risk being with someone who takes the initiative to court you
but may not be the right one for you?
Of course, in an ideal world, it'd be perfect if Mr Right(at least,
one by your definition) courted you, but you've to realise not
everyone is fortunate enough to live such a charmed life.
As for socialising, I don't suppose we can help you much, but
perhaps you need to learn to open up to others? You could always
start with your friends, if that helps. No disrespect, but if you
think you can't socialise well, what difference does it make
whether guys courted you or vice versa(I mean most guys - even
those who take the initiative - wouldn't like to be with a girl who
only gives monosyllabic answers, for instance)? I mean, being able
to socialise well really shouldn't be used as an excuse when it
comes to taking the initiative IMO(unless I misinterpreted you, I
believe you claim to not dare take the initiative - besides the
fear of rejection - is down to your social skills?).
