You sound like every teenager in the world to me. I was like that myself and so was everybody I knew. And later, when I had a job, for years I had a repeating dream - the alarm went off, I hit snooze, slept for a couple of hours and then my boss came roaring through the door, yelling "Are you coming to work or not?" And then I woke and looked at the clock - it was only 5 minutes later, not a couple of hours.
Well, my point with that is that you're not alone. And a louder alarm won't help - my cousin installed a fire alarm and set it to go off at 6a.m. - she and her husband slept through it while it rang for an hour. They had very unhappy neighbours.
The thing is, you have to decide. Are you going to take a run at this thing? How long will you suffer - years or months? If we're talking months, I would hope you'd get a tutor and go for it. You will strengthen the "do-it-anyway" muscle. Then you can do what I did - I walked away from that school as a graduate and absolutely refused to look back.
You can do it, if that's your choice. I doubt that you would regret getting this out of your way forever. You can come back here and we'll support you.