I'm homeschooled and feel like I'm wasting all my time, suggestions for getting into a productive routine?

I'm a 15 year old girl, homeschooled... I'm a serious pianist, cellist, and oboist, and I'm in a choir, youth orchestra, and local symphony orchestra. I should be practicing piano 3-5 hours a day, cello 1-3, and oboe 1. Three days a week, I don't have any scheduled lessons/rehearsals (I've got everything packed into two very busy days)...and I end up completely wasting those days. I need to be doing academics, as I am going to an arts school in the fall, with academics. And I end up practicing piano 1-2 hours, cello 15 minutes or so, and oboe like once a week for 30 minutes. NOT GOOD. I sleep late, like 10 or so, and spend time just browsing the internet, playing stupid games on my iPod, watching TV shows on youtube.... How can I get out of this unproductive rut and get stuff done? I also should exercise, but I have zero self motivation... I feel like I'm wasting my life away and want to find a way to change that! Any suggestions, or schedules for me to try to stick to? THANK YOUUU