Lol, I am having the same problems at the moment, my family is going away again for the second time this summer without me but oh well...
First *hugs* your life sounds a bit rubbish at the moment from what you have written.
You say that you have to talked to a few friends through IM is there no oppertunity for you to meet up at all? Even if its to go to a film, or just a bike ride or something like that, at least you would be doing something and out the house.
The holiday thing sucks ( and contray to belief this may not be your fault) just because you didn't know about the injection I find it a little off that your family didn't mention it to you...But there must be a bright side to it? You now have a bargining tool with your parents perhaps, I don't know. just try not to focus on that, and try not to get to bitter. Being bitter really isn't going to help the situation, and will probably make you feel worse.
Hmm well you are going for AS results tommorow right? Check the notice board and see if they have information on any club activities that you can join when you go back. I know it isn't immediate but its something to look forward to and a way to make new friends and pick up new skills.You will also raise your self confidence doing this, as you will have learnt something new. And it should help to aliviate the boredom.
You have to remember that you arn't nobody and that you definitly have people who care for and love you. To them you will never be just a shadow, and they see you from the outside so you must have special qualities.
Saying you want to learn and instrument, take up a sport or a hobby, go look! To learn those kinds of things you need to go find out about them from your local area. That will take you out, give you exercise and some purpose and something to be working for.
To be fair, and I feel horrid saying this, you can't sit around and wait for everything to be handed to you on a golden plate. If you really want to do something make an effort, and don't expect others to sort it out for you. I really apoligise if that hurt you, but I think you need to hear it. You know you are depressed/bored/lonley and finding it hard to have enthusiasm, so try and attempt to do something about it, instead of sitting there worrying about it, okay?
Alright I hope this helped and I wish you the best of luck.Hope your AS results come out well.
Keep us posted.
xxx