A well written post.
I'm 63yo. As a teenager I had some big hangups I wont describe. I was teased and fell in a big hole. I didn't know it but I also had mental issues to do with 1/ family genes 2/ a near tragedy years earlier. These issues remained undiagnosed for over 40 years. So for that time working as a RAAf airman, prison officer, ranger and investigator I struggled to attend work and keep my head up. People were and still are my challenge. So based on all that I'll guide you through a few things one by one.
Body image- The good news is the older you get the less it matters. The older you get the more focused you get on friends and lovers accepting you for who you are NO MATTER who that is. School era does not reflect that at all. There you are among largely immature opportunistic kids that seek only fun. In a short time in your life you will break free from that environment and you'll find a different world- the working world and adults.
People- The adult world isn't without its unique problems however. It is a dog eat dog world. The stronger you are the less hurt you become from bullying, taunts, nastiness and judgements. So, I developed ideas on what I lacked to cope with this.
Google and read the first post
Beyondblue topic fortress of survival
Beyondblue topic fortress of survival part 2
There you will find a way of screening strangers so you don't let into your world those that are potentially hurtful/toxic. It's a defence many have but you and I have to develop. Once you have don't that life includes friends that have proven they are worthy of you love and care.
Confidence isn't easy to grow. You can get it from other people and achievements but the best person to get it from is- YOU. How? Again google
Beyondblue topic the best praise you'll ever get
Planning your life- It is no different than planning to build a house, save money, foundations, frame... So develop short medium and long term plans. Plans for one week ahead, 6 months, 5 years and so on. Try to stick to it.
Worry- one of the things I detected was worry. If you worry about falling behind in your studies how will worry help you? Worry produces nothing but ulcers.
Beyondblue topic worry worry worry
So, based on that and your plans...your first short term goal should be to get to school (not worry about your studies) the second goal to ignore bullies and the third goal for the day is to appreciate yourself as a kind person.
I hope that help. repost anytime