Motivation after a long hard day…?

I need to lose weight before it gets worse. I am a teenager and i am overweight, and have a very low confidence level, etc. from it. I am really wanting to lose weight, and im trying to eat healthier…even though sometimes i find it hard to. I also really want to go to the gym and run after school everyday. But i go to an arts school as a musician, so on top of waking up early everyday and going to school, i have long rehearsals after school, along with honors hw. These all are a lot of excuses…i know. But how do i find the motivation to do it everyday? Thanks for the help.