Motivation comes from within. I can tell you all kinds of awesome things to get you motivated, but if you're not motivated to do them you won't. In the end it comes down to you, deciding to do something. Do something when you probably would rather not, or would rather do something else.
That's it. You just gotta get off your ass, that's all there is.
Nobody here can say anything to force you to work because I'm sure you've heard it all before. But think of the time (and money, I assume) that you're wasting by not working and force yourself to do it. Don't worry about stuff in the distand future; be productive and change the things that are in your control now.
Healthy eating at regular times (no snacking, especially not at night) and exercise will help with your sleep pattern. Also, stop indulging yourself and sleeping in; even if you're exhaused, force yourself to be up at a certain time every single day and don't nap. Your body will adjust in a week or so when it gets tired enough to sleep earlier.
If you want to do exercise, could you ask your friends to go with you? Even if it's just jogging, swimming or to the gym you could be active and be with people you like. Failing that, you could try to do these things yourself anyway.
I am kind of going through the same thing. What motivates me though is seeing my family and people I don't even know struggle. The family I have that did not finish school aren't doing so great today so it motivates me to do well so I don't end up in that same position. Also just making goals and stuff might help. Exercising like *Joe-Maccer said can definatly help. Just a walk or jog every day is a good start (: