Hey - it happens. You probably spent less hours working on games every week in the past than you do now, officially studying game development; and you probably just did the "fun" stuff, rather than seriously buckling down and learning useful skills no matter how dull the process might be. If you end up spending too much time on a hobby and taking it too seriously, it's natural to want to do something else with your free time.
The fact is, lessons are just less interesting than playing around with tools and technology when you've got something cool to work towards. Also, if you've been working on this stuff yourself, you might find the material in the first year or two of the course very easy.
You may also feel complacent about 'becoming a games developer' now that you've got on a course that says it'll make you one. (If that's the case, you might find it interesting to ask what percentage of graduates go on to work in games. It won't be 100%. Some people will drop out along the way, and some people just won't be good enough when they graduate. Some of your friends on the course probably won't make it. You might not.)
Anyway, however it happened, the reason you had to make games has disappeared. You've got to find a new one. I don't know if it'll work for you, but consider taking part in challenges like Ludum Dare 48 to see how you measure up to other game developers, including professionals. That'll give you a chance to test your skills and see how far you need to go to match up to the best. If you're at all competitive, give this a shot - it might motivate you.
Something else that'll help is to hang around people who make games all the time. Whether it's on this forum, on IRC channels (like the Ludum Dare channel) or anywhere else, the more time you spend talking about making games with people who make games, the more you'll feel inclined to do so yourself. It's a simple trick, really - we're social creatures, so we adopt the norms and expectations of the people we spend time with.
Finally, just go looking for cool things you could make and reasons to try them. Do you like thinking up game ideas? Who doesn't, right? When you come up with one you like, try bashing out a prototype over a weekend. If you think of a way to improve a game, try modding it in. You don't have to commit lots of time to this stuff - you can knock out basic cool things in a couple of evenings, or a weekend.
In the long run... game development probably will never be quite as much fun as it used to be. But as you work on game ideas and so on, occasionally that old passion will flare up and take over. It's not gone - it's just sleeping, waiting for you to get back on track