welcome to a2k ikkkkuh
It could be depression.
But you know something, I've been feeling really lazy for like that for the past two years or so. And I'm definately not depressed. Save for one or two minor things, I absolutely love everything about my life.
If you're having fun with friends on weekends, it's probably not depression. With depression, one of the main signs is that you don't enjoy any aspect of life too much.
It could be general anxiety or have been triggered by a specific anxiety. For me I know that the laziness all started with this one lab class that I was having a lot of trobule passing all the labs. If you can't finish every lab without less than a 1% error, you fail the class. I stopped going to all my other classes, slept all the time but really focused on that one lab, didn't do much work otherwise and the laziness didn't go away even after it all worked out. But now I think I'm generally anxious about med school.
Are you maybe anxious about college? Trust me, I was worried about college too but it turned out to be even more fun than highschool. You have so much more freedom, so much less busy work, and as long as you keep up with the material, you get more free time than you ever did in high school. And I think the teachers grade a lot easier too. Just make good friends early on and keep up with the work and you'll have a great time.