I think you should stop looking for an explanation of why you feel like this, and start putting energy into stopping yourself in the future. I never got on with counselling or therapy - why would anyone want to relive everything bad that's ever happened to you?! you should try and treat everything like a learning experience, because that's what life is. I believe in reincarnation, so this may be a bit weird or biased, but I believe each life we live is there to teach us a lesson.
I have most definitely been where you are now, I actually got bullied by an entire year group, based on one bitter ex boyfriends lies (who still works part time at the local supermarket.) I rose above it, I quietly ate lunch by myself, looked down my nose at anyone who laughed or said something horrible, or just rose my eyebrows and walked away, (every second wanting to run away and cry in a dark corner somewhere). Within weeks people were taking my side because I regained respect for myself, and so they did too.
The only person's opinion who matters is yours. If you don't like something about yourself than change it, if someone doesn't like you, it's nearly alays jealousy. It's hard to believe when you have no self confidence, and to be honest I don't always believe it - but there are a LOT of people out there who envy others and put others down to feel better about themselves, the more people I meet the more shallow self obsessed people I see, and I disregard them. The people I know that are nice I respect, and their opinion counts. The first girl in the year group who was honest and said that she still liked me, and everyone else was just following the "popular group" because they didn't want to get bullied too has been a good friend since that time. Also, since that time, all those people are unhappy with their lives and try and apologise to me in the actual street. But... I JUST DON'T CARE!
You should see yourself in positives, being sensitive to criticism is better than being self possessed and arrogant. Being different is so much more fun than going with the crowd. Your true friends are those who accept your quirks, and if that only leaves you with 2 friends - it's better to have 2 true friends than the approval of 30 acquaintances you won't know in 5 years time. Concentrate on what YOU want to do. Find out what you like and study it, find passions, embrace what makes you different, because when it comes down to it, we're supposed to be unique, and even the most meatheaded sports mad man will cry sometimes, and feel insecure a LOT of the time (trust me I've seen and heard it!)
Anyone that spends time making you feel bad has too much time in their own lives. And some of the greatest minds and most famous people were misunderstood in there own time (Van Gogh, Kurt Cobain, Loads of scientists!).
You're not unwell, you just think differently, like I and lots of others do - and I've embraced it!
It's difficult and I still have a long way to go now too, but I know respect only those who care for other people, and listen to opinions only of those that I respect.
It's a bit of work, but you might want to try MOODGYM online, it's a way of explaining the negative thought patterns that lead you to feel like this, one of them is where you put thoughts into peoples heads that aren't there (Believing people don't like you when you have no reason to think so.)
I believe people like us were put here to make a difference in the world's way of thinking.
Also, I get bad back from tight neck muscles, try giving yourself a bit of a neck massage if you don't want to ask a masseur (I personally hate havng people touch me like that when I don't know them!) Just start at the base of your skull and stroke firmly down, and press on the knots in your shoulders until they disperse - hurts like hell but can relieve some of the tension you're feeling.
Sorry for the mammoth essay, it just makes me mad when I see people who dislike themselves when they have no reason to - having been there myself!
I am also the odd one out in my family - but again - that's fine by me!
As for your sleep - there's nothing better than natural remedies!
Lavander, Bergamot, Neroli and Valerian capsules or Bach's rescue remedy (night) combined with classical music: You'll feel like an old person but if you do this and go to bed the same time every night after a week or two you should start to feel better.
I know that there can be a temptation to replay things in your head when you're in the dark and quiet - but don't! Even if it means reading until you can't hold your eyes open anymore, just try to keep thoughts neutral. Also, having a tv or computer on even in standby has these little high waves that will disturb your sleep.
Hope you start to feel better soon, look at this way, people you don't even know care enough to reply to your posts. The people in your life do care, it's just they don't know what to do to make you feel better, and they probably feel like it themselves half the time too. No on eis perfect, and it's foolish to try to be!
Hope the essay helped a bit!