yes, its very normal!
its too late to back out now though!
try not to think about the negative things....giving birth is a means to an end.
it hurts, yes, but is a different kind of pain to most others...it comes and goes, you know why you are having the pain, you can (by watching your contarction times) almost predict when the pain will start and end, and get a little breather in between each one...
by the time you are feeling anable to go on, your baby will be born, and although, its generally not instant, the memory of it becomes distant and soooo worth doing!
birth can be a really amazing experience...it can be empowering, and positive.....
try looking up some nice deep breathing exercises and listen to your midwife.... she should be able to teach to to ride the waves of every contraction through breathing techniques....
i've done it 3 times now, and oddly enough, really like giving birth!
try to focus on all the positives around birth. people always love to tell horror stories...block them out of your mind, and listen to your body.
good luck when the time comes! x