I’m in Year 11, I have had this one main bestfriend for roughly 11 years now. We went to the same primary school but went to different secondary schools a few years ago. We still kept up our friendship, it’s unique and was perfect. But now I feel like she is drifting away and I can’t do anything about it, she is so popular and has loads of friends, some really close who also call her their bestfriend. This is mainly jealously, I know. But still, I have 2 friends I am always with at my school currently, I’m extremely shy and I think I may have social anxiety which is ultimately why don’t go out or make any friends. I am so so scared about moving onto sixth form or college in summer, because I will have nobody with me which I don’t think I’ll be able to cope with and I think that’s why I keep “putting off” applying to anywhere because I just don’t want to properly grow up and go into the “real world”. My shyness is destroying me, I won’t go out anywhere and I know I won’t make any friends when I leave school too.
There is a difference between being shy in the conventional sense and having social anxiety which will obstruct your ability to have *any* relationships in your life. One of the unfortunate realities of life is that friends come and go. You will go to sixth form and not see people from school ever again, go to university and not see people from sixth form again, and get a job where you'll never see many of the people from any of these places ever again. Life is like that, nothing permanent, ever changing. That's why it is important to build a basis of confidence now. Don't worry about being alone, instead think about how you are going to establish friendships when things change again. Make yourself an interesting person, take up hobbies, interests, these will bring you closer to other people. Also become aware that having lots of mates isn't really everything. Many people have plenty of friends but are not happy because happiness is ultimately something that comes from within, in your own attitude. If you are constantly down about everything (like assuming you will not make friends in the future when you don't know that) you will see the world as a difficult and unfriendly place, whereas if you adopt a positive outlook you will not only probably attract people towards you, but even if you don't it will not have such a negative impact on you. If you truly feel like you have social anxiety to the point where you can't make any friends, I'd recommend making an appointment with your GP who can direct you to a professional who can help you talk through it. Some people are crippled by social anxiety to the point where they cannot function, and at that point you need outside help to put you on the right track.
I have a sort of similar case as you. My best friend has lived in Japan since I started middle school. We really are drifting apart so much, yet I still consider her as my closest friend. It hasn't prevented me from making friends, though. Albeit, I sat alone at the lunch table for the first few months of school, but I eventually made friends. I am shy around strangers, but I can warm up to others over time if they're the right person. So, that's what I recommend; finding the right people to warm up to. I don't have any interests in going to social events and such, but I still make it by with a few close friends (which is all you really need, in my opinion, since a few good friends is better than a ton of "meh" ones).As for putting off applications, I get that too. I applied to an academy that I was later accepted to, meaning that attending this school would cut off all of my relationships I had in my home school. I was reluctant to choosing to go there at first, but in the end I went because I valued my education more than my social life. I think it would help to focus on the actual learning part rather than having friends (I probably sound like a loser). If you find learning important like I do, it shouldn't be as hard for you to make yourself apply for your education. If you still want a way to find friends, if you're good at drawing, music composition, etc. bring a sketchpad/sheet music to school and just sit there while doing your thing. You might attract someone who is interested in your work, making a good conversation starter. Or if your not big into talking, just let them watch you.