I think yr complicating your life by bringing in lots of different factors, you dont give yourself a moments rest, but yr nagging yourself with irrelevant situations. Focus on staying in the present, not the future (what if, etc). It must be hard for you to stay on course when you bring in so many decoys! Cut the mental clutter, and focus on what is. Right now. And plan the day before, getting ready, (homework, deodorant etc). As for shaking, be who you are, and know you are good enough, you dont have to pretend to be cool if you're anxious. Just be okay with being a person who feels that sometimes, others will cope. And if they dont? Well, thats just too bad isnt it? Yr worrying too much!
You have to mentally train yourself to not "think" of the "what ifs." When you catch yourself, stop! Stay in reality.