Where's the motivation?

I haven't been or felt this lazy since last summer, and I'm genuinely worried it won't go away.  My future,  hopes, and dreams depend on my grades, and right now I absolutely can not focus on anything.  I've noticed, each time I try to finish my schoolwork I end up procrastinating somehow.  Even now, I have my neglected English essay open in another window and I'm unconsciously doing everything I can not to work on it.  I hate feeling so useless but I can't seem to get my drive back.  Hopefully, this is just a typical teenage phase and I'll go back to normal soon.  If I don't, I can just see my ambitions and my entire future going down the drain.