You CAN do it!
Somewhere, in the past week, I heard labor described as "pain with a purpose".
You know that there is going to be an end to the pain. You can't labor forever. And at the end, you meet your child. It is totally different, IMO, than any other type of pain.
And usually, when you feel you can't last another minute more, it is time to push.
My experience with "pain relief" in labor is that all drugs such as Nubain or Demerol do is to make you disoriented, and disconnected with your body. For me, at least, they didn't really take the edge off- they just made me too doped up to complain about it to the midwife, doctor, or nurse on hand. Great for them, not great for me. I was dizzy, the room was moving, I lost track of time, and the order of things, voices were too loud or too soft, and I wanted to throw up.
My completely unmedicated births were WAY better, because my body coped with the pain the way it should (going into labor land, natural endorphins, etc), and once the baby was out, my head was clear.
I think that "Birthing From Within" is a great place to start, in clearing your head.
Good luck. I believe in your ability to do this!