If you're not already "depressed" it sure sounds like you're headed that direction, and while I'm only a few years older than you, I've been going through something very similar. The daily routine of getting up, getting money, buying pot, smoking all night long in a car with a few buddies got old fast!
I did exactly what alasdair mentioned above. I had to actually look at myself which is something I hadn't done since rehab years ago. Taking action is the most important step! You mentioned skating is one of your biggest hobbies yet it's become dull and boring. This can be tied directly to depression, as it does things like make you lose interest in everything and everyone. Glad to hear you're getting a gym membership though. For me at least, working out has always made me feel way better and I feel as if I can think more clearly after a good workout.
Best of luck to you!