You're not that far off. I think you just need to take a sheet of paper, hold the corner curled over, and look at it. Draw a picture of it. Draw what you see, not what you've made on the screen or what you think it should look like, and I think you'll see the difference. You have a curve where you need a straight line, and abrupt corners where you need smooth curves. You know how to make the shapes.
Seems like I remember some nice examples being available for download
in the Adobe Exchange. Just search page curl and check Illustrator
as your application and you should find what you are looking for. It
would be easier to modify one of those to fit your taste than doing
one from scratch.