Hmm.. seems like you are experiencing low self esteem.
Hope you don't mind if I just give my opinions k..
You don't have to be outstanding in terms of looks, studies, etcs.
Remember that there can only be ONE top student, a few top
atheletes, etcs. In the end, it is these type of people who are
more stressed because they constantly live in the fear of being
surpassed. This is why the term 'lead a simple life' arises.
People making use of each other.. There can only be so much
unconditional love. The only unconditional love is parental. Maybe
try not to see it as making use of each other.. It is human nature
to 'mutually benefit' each other, and I guess this behavoir appears
in friendship as well.
As for the issue about the gal.. Well, a lot of time, a lot of
people have told me that it may really sound cliche, but are you
sure you can use the word 'Love' when maybe it is just a crush?
Because like you said, she treats you like shit, so is it really
worth it?
Well.. no one cares about you? You still have your 'mushy gang',
and I am sure that there are a lot of people who want to join that
gang but are not able to, while you are one of the privileged few.
Lucky you 
Sometimes, the easiest way to boost your self esteem is simply to
do some volunteering work, for example at the Old Folks home, the
things you do may be so little, but when they thank you, it makes
you feel useful and important.
The problems you are facing are not chronic, therefore all you need
is to look more kindly upon yourself, realise that you are unique,
and I guess you'll have to accept the fact that input does not
equals output, so when you say you give people attention they treat
you like glass, remember that glass is beautiful, without glass
there would be no windows, but walls only.
As for studies, I am sure it can definately be improved.
Cheer up !
