Sounds to me like youve had a pretty tough time and although you were very young when your parents left, i'd say its probably affected you more than you think. You said you have had your heart broken and no-one really knows the real you. It sounds to me as though you have abandonment issues and need to be loved and feel loved. You may not like yourself and thats why you change your personality to fit in with others and why you have eating problems and cut yourself.
I can relate to how you are feeling (with the self harm and eating disorders, ive had eating disorders since I was 17...I'm now 23).
The only way that you are going to get through this...Is be strong for yourself. When you suffer from depression and you are in so deep that you cant see yourself getting out of it, the only person who can truely help you, is you!
Posting on this forum is a good start to helping yourself. Beleive me, there is so much fun to have in life...So many things to see. You need to think about the people who have hurt you and say screw you!!!!!!!! I'm going to make somthing of myself....I'm going to see the world....And i'm going to live life to the full!!!!!!
As for changing your personality arround your friends to fit in...The great thing about having friends is that they all have different personalities and different opinions and thats what make you click, I think that if you act yourself people will get to know the real you and your friendships will become stronger.
Your depression will pass.....But you need to give yourself a kick up the backside and say...'hey i'm better than this....I'm going to go on nice vacations...Hang out with my mates...Get a good job...And so on..!'
you can be anything you want to to be.....But in the process...Always be yourself!
(i'm walking proof that this can be done!)
wishing you all the best! Xx