Welcome here to the Forum, where you will find there are different way of looking at things.
Your post paints a clear picture of you life and feelings, you write well. It also points out very clearly you are a sensitive person -which is not a bad thing at all, and that you receive little support.
Also you have a circle of acquaintances (I would never call them friends) who are cruel and unfeeling.
Given all of that on an ongoing basis it is hardly surprising you see yourself in a most unflattering light -and also that you are probably mistaken. You are smart enough to come here for other people's advice, so you are not dumb.
I've no idea how pretty you are, but you have to realise pretty is something others see, not you. Your view of yourself is colored by your unhappy mood. A radiant smile can melt a heart. Just a moment of happiness and that smile can come out.
You say you are not a good freind, but you also say you would do anything for friends - I believe you and that is praiseworthy and is indeed being a good freind. All you have to learn is which ones are in fact friends and worth your trouble.
Talking about your problems is something everyone needs to do, the trick is to find someone reliable. If you are still at school is there a teacher or councilor you can have a talk with? There would be no repercussions, nobody breaching confidences. Is there anyone like that where you are? If not school in family perhaps, an auntie or other?
I don't think you are attention seeking, your unhappiness is genuine, and that is a sad thing, life can be enjoyable. Leaving aside "friends". parents and everything else what do you enjoy? A game, series of books or comic novels? Music perhaps, or maybe the beach if you are close? A pet? What would it be?
Doing things you are good at, or simply enjoy, is good for you. This is something I do and it helps. Do it long enough and you start to get the feeling you are worth something, a person entitled and deserving to have enjoyable things in their life.
If I was you I would not want to be anyone else, you sound the best of everyone you have described