You said you often have too much homework and feel tired. I think you can eat red food or wear red clothes. Red represents power and strength, so it can cheer you up.
You also said you feel much too stressed and cannot sleep well. Maybe you can sleep in a blue bedroom, as blue is the colour of calm and peace.
If you're shy and not confident enough, I suggest you use yellow stationery. That's because yellow is the colour of wisdom and success.
