It's okay to ask for help, with anything. People don't see you as a weaker person and the majority of people are happy to give you a hand.
Don't waste your time on people. If it's obvious that they would much rather hang about with others don't take it personally. If you make an effort with them and it's not returned, you don't need them in your life.
Get higher English. You might need it some day.
It's okay to have different opinions on subjects from your friends. Don't be shy in voicing them.
Read as much as possible.
Stop worrying about everyone judging you for every little thing. Your hair, clothes, things you say. No one is judging you. In a few years time you'll never need to see the ones that do.
Be confident in yourself and everything you do.
Talk to the people in your classes that you don't know. You'll bump into them later in life.
Wear your hair down - literally. Stop worrying about it being frizzy or a mess. It's not! Wear it curly too, you suit it, it requires less effort and doesn't damage your hair.
That YouTube lot are important. Keep them around.
Stick at it with Guides - You'll miss it when it stops.
You'll meet boys who are actually worth your time.
Eat lunch. And breakfast.
Your health is incredibly important. Stop putting off going to the doctors.
Start watching Doctor Who.
Go to bed early sometimes. Staying up 'til 3 every night is not good for you. You'll feel better after a good night of sleep.
Don't worry. Everything will turn out okay. :)