I had this trouble for a long time. I think its all about getting yourself into an appropriate routine. Its probably a good idea to get a blood test to check for things like anemia etc just in case.
I think the best thing is instead of an alarm have the radio come on or something, that way you dont turn it off, but you dont go back to sleep. Have it quite loud so you wont be able to sleep, you will stay in bed for a bit but then eventualy feel the need to get up, or at least sit up in bed.
Go see your GP.
There are multiple things that could be causing it (one being laziness!).
I have this. I'll quite happily just sleep all day, and if I ever do have to get up before 12 I'll find myself drifting off around 3/4 and then again after dinner. It's pretty stupid.
im exactly the same, i love sleeping
Your Doctor will order about 6 blood tests. One for red blood cell count (anemia), one for white blood cell count (high levels indicate infection), thyroid function test, liver function test, urea (sign of kidney failure), blood glucose (if high indicates diabetes) and a couple of other teats.
Assuming that your bloods are in order then it could be depression. Or it could even be M.E. I suggest you don't touch junk food, alcohol or tobacco. I suugest you drink plenty of water, fresh fruits and vegetables. Also get protein from milk, eggs, soya, lean meat and fish. Also exercise every other day. This does not mean spunking money in a gym. Get a mountain bike and ride it on green routes, bridleways and use it to get to college or work if possible. Also swimming once or twice a week is very good for you. Jogging is OK but it is boring and puts alot more strain on your knees and ankles than cycling. Brisk walking is better. Also it might be worth taking a multi vitamin and minerals tablet each day. The supermarket own brand is good enough.
I think when we're teenagers we all kind of go through this patch - I went through it for a looong time. I think the reason is usually not something medical, it really is just laziness.
What happens is, when we have holidays or something, we'll take advantage of the free time and just sleep. Funnily, we think we'll be fresher when we slept more (because you 'getting rid' of more sleep, but in fact it actually does the opposite - you'll want to do the same thing the next day, and then it just carries on and on. If you just limited yourself a certain number of hours from the beginning and stuck to it, it'd be fine.
The reason you wanna keep sleeping is because you slept so much the day before. The best way to get out of it is to, one day, just get up early (having slept reasonable hours. about 8). When you wake up (and in fact during the whole day) you'll feel like sleeping - but don't. It's kinda like withdrawal symptoms. If you stick to it, you'll be fine within about a month.
In Urdu, there is a little expression "susti kaa ilaaj chusti" = (~the cure for laziness is becoming alert).