Is your son sleeping in or is he going to bed early? My kids loved to sleep in as long as they could when they hit those teenage years. I'm sure part of it was their growth spurts, but part of it was being able to procrastinate getting up. Why does he think he sleeps a lot?
The waking up thing could also be due to their overactive brains. They have a lot of things to stimulate them all day with all the electronic devices, etc. My son stayed up late a lot, not because he couldn't sleep but because he wanted to play games.
A physical is always a good idea, especially if he hasn't had one in over a year. But also make sure that you check in with him from time to time on how he is feeling. Wait til you are in the car as boys talk better when they don't have to look at you. Then ask questions that cannot be answered with "yes" and "no." E.g. Which teachers are the most demanding? Do you feel like you are able to keep up? or Who do you hang out with the most at school? What do you like in common? and Have you thought about what you'd like to do after college? You used to talk about being a ____. Are you still interested?
Check to see how he answers these kinds of questions. If he is depressed, you should be able to pick up on the way he talks about stuff.