Am I Pathetic? Help I need to know whats wrong with me?

Lately I have had so much on my mind and it is really getting to me. I have a happy family considering only my parents and my sister. But I also have two other half brothers and two other half sisters, j, s, e, and a. I don't see e and a much (my older half sisters) because they are involved with dodgy people so my parents have said I can visit them and they never come see me but that doesn't bother me much. But j my older half-brother is a heroin addict and I never speak to him but sometimes I see him around but I turn around to avoid him because I don't know what state he is in or who he is with. Some times I feel like I am almost scared of him but I don't know why because he is my brother and before he left home and got on the drugs we were really close. My other older half-brother is anorexic and some times I generally wish he was dead. I know its a horrid thing to think and it confuses me but with him being anorexic it worried me when i was younger but made me more angry at him than anything because it made my family get all stressed and I didn't fully understand the illness but just hated him for being the way he is. My best friend tried to tell me I remember but I have a mental block and I really can't make sense of the fact that it is an illness and its not his fault because that just seems like an excuse for what he does and him having no respect for others. When I got to secondary school I fell out with my best friend and we still don't talk and I constantly get asked about it because when we were younger we were well known for been such good friends. Then the next year one of my closer friends, g started getting really unhealthily skinny and it was her best friend el who said to me that she was worried. This then escelated and it ended up that this girl Ellie found out and decided to spread rumers saying that I had told the school that she was underweight and anorexic because she had to go to the school nurse when I didn't and I started getting people I didn't know coming and asking me about it. She made all my friends ignore me and Ellie began sending me messages on Facebook sending me all this abuse saying I shouldn't have any friends and that everyone hated me which made me feel really shittt and really hating myself. I made friends with this girl who was weird but gave me friendship and when I was really angry i hacked into ellie el and g's email account and found things from all of them saying that they hated me, thought that it was all me saying this girl was anorexic and then saying that my whole family was 'not normal' and my sister, y is the only normal one. I felt like dieing at that point but then when I was really upset the girl i had turned to would take advantage of the fact that I was vulnerable and I would tell her things I shouldn't have and she spread them. I lost friendship with this girl but I am not friends again with el and g but although I am 'friends' with Ellie I find it really hard because she takes this micky out of me and says 'oh i love bullying you' but sarcastically as if it is a joke and then i would act as if I know she isn't serious but everyone knows that the things she says are true. I am now constantly parnoid that she is doing the same thing again or I am going to loose el and g again. I am fealing really weird in myself and I don't know if it is to do with any of that stuff but I like to blame it on that to give it reason. At the moment I am doing exams two years early (I am 14) and I don't see loads of my parents but some times I suddenly feel awfull, like there is no point in life and I leave class and go to the loo's and cry but I don't know why. I think that really I feel like that all the time its just most of the time I am just trying to make people think that I am great because before when I fell out with el, g and ellie they said that I was depressed. Recently though when I get upset which happens a few times a day i have started scratching my hands really hard so the skin comes off like carpet burns. I have loads of scabs now and my hands look raw and people keep asking me what happened. I started saying that I just woke up with it but then it seemed like people were getting suspicious so i said it was carpet burn. I can't tell my parents because I feel like I have to be better than my siblings, I don't know why but that pressure is there. I also know that they will just think it is attention seeking. I want to stop and I have tried and still am but I can't. Everything is turning into a lie, me pretending to be happy, my hands, how I feel and some times I wish I would get caught so I could talk to someone but I know that that will never happen and even if it did I would just lie my way out of it because I don't want to hurt my parent. What do I do? Am I pathetic? Am I depressed, or is it stess or just hormones? I need advise :(