From the Desk of Harry Potter, Head Auror
Ministry of Magic
It may surprise you to know that you and I are very much alike. I attended a muggle school in my younger years, and I was often picked on for my reserved nature, my appearance (wearing your cousin’s clothes when you’re about 10 sizes smaller than him is not exactly flattering) and the odd happenings that I inadvertently caused due to my magical abilities. Even my teachers were not particularly supportive individuals (come to think of it, certain Hogwarts professors were no better).
I admire your ability to remain calm (a skill I am somewhat improving upon with age) as well as your keen sense to realize when your friendships are unhealthy. You sound like you have all the strength you need within you. Most people (both magical and non-magical) do, although it takes some longer than others to realize it.
The best advice I can give you is to stay true to who you are. Only you and your best judgment can decide those who are friends and those who are not. As long as you stay true to that, you will eventually find yourself connected with good people. I didn’t have friends until I was eleven, and they’re still my friends to this day; Ron often jokes that it’s my fame that keeps him tethered to me, but Hermione often politely reminds me that the two of them always admired that I stayed true to my convictions. Even if they thought I was absolutely bonkers when I did.
And, when you’re at your lowest, don’t ever hesitate to nibble on some chocolate and practice your Patronus Charm. Strength and patience like yours can produce very powerful magic.