I'd like to welcome you here to the Forum, it is a good place to come to as you often find others with similar problems and can see what has helped them.
First off I'd have to say counting you blessings, "...two loving parents, loving siblings, a good education and stable finically..." can sometimes be of no help at all. The mind goes its own way and logic like that simply does not come into it.
Having to spend your time worrying about the reactions of others, joining groups and being judged, and not having someone to talk seriously with makes for a most unhappy life - and you, like every person, deserves better.
May I ask if you have been to anyone and talked over your feelings? I guess it might be possible you have depression or anxiety as some of your thoughts remind me of the state I was in. Bear in mind please I'm no doctor, just someone with those illnesses. If that were the case the sooner it is identified and treated the better. Recovery is quicker.
Naturally I went the other way (typical for me) and told nobody, a mistake that simply made things that much harder later on, and I was most unhappy in the meantime til I started to reach out.
If you have not told anyone then can I suggest you do? It was how I started to improve. There are a few options you might consider.
One or more members of your family might be good - any you'd feel more comfortable with there?
Most schools have a councilor who would be used to problems like you are facing, as might your GP. If you want to seek advice outside your normal circle I'd suggest the Kids Help Line, who have trained professionals you can talk to more than once, they are experienced, practical and understanding. You could use their phone (1800 55 1800) anytime or else their web chat service
Sometimes not being face to face but just typing or on the phone can be an easier start.
As for others being worse than you, this place, Kids Help Line and all the rest are here for people like yourself, you are as entitled to the best help we can offer the same as anyone else, so don't worry about that.
Getting to the point of being comfortable around others is possible, and within your reach.
Please let me know what you think