Interesting question phantomj. Some great suggestions already. The thing coming strongly right now is natural citrine to help with congestion, to clear the sinuses and stop coughing. If it doesn't seem to work at first, move it around to different places, including out away from your body. Citrine helps take headaches away for me too. An amazing stone. I usually use citrine crystals, but use whatever feels good to you. That's your body telling you that, regardless of analysis, a particular stone resonates with your particular body.
Clear quartz for energy. It has a pure, powerful zing to it that can help one get off the dime. Relax and ask it to fill you with its energy to get you over the hump at the end of a period or match. Stones easily work from a distance as well, so you could carry a small bag inside whatever you use to carry things in. Safe in a locker is fine. A friend could hold the bag, etc. I ask stones at home to help, which works well too.
Smoky quartz might help with butterflies. It's great with grief, sadness and going within to learn more about oneself.
For injury, as anything, go with what feels good to you when you look at it or hold it. My main stone for this is a silver-rutilated, clear quartz sphere. I'm not sure how I could have done the physical labor I have without sleeping with the sphere between my legs. Totally awesome!
For flexibility, try rose quartz, a relaxing, soothing stone. Calcite just came to mind as well. Place the stone against super stiff areas and nearby while stretching.
Try grounding stones for balance. You know the difference between trying to balance with the soles of your feet and feeling your center. The key to balance is remaining grounded. Black tourmaline, obsidian and hematite are a good place to start. Or quartz containing black tourmaline or hematite. The smoky quartz grounds well too.
There's a lot of quartz here. It's reasonably durable, easy to find and plentiful. Study focus with a clear quartz laserwand.
Once you've worked with stones awhile, you may begin to trust whichever you are drawn to, put them in a pocket or keep them in mind (large or fragile stones) and go about your day.