As Sus said- just go with what your body tells you. You will know what to do...your body just seems to take over. I did have intervention in my labour (I was induced amongst other things) but I got to 9cm all on my own with no drugs. Yes, it did hurt but it wasn't excruitiating pain the mistake I made throughout that time was closing my mind off to the birth and making myself believe I couldn't do it. I think this added to the pain (my bubs ended up being posterior and I had an epidural) and I was screaming for an epidural which I NEVER wanted the whole way through my pregnancy. I really wanted a natural birth with no or as little intervention as possible. This clearly didn't happen for me. I do want to add though that if things don't go to plan as they didn't for me don't be disappointed, as long as you and your bubs are safe and well in the end that is really all that matters. Next time I am aiming for a natural birth again but if things deviate from what I originally wanted I think I will be prepared this time. Another thing you could do is read some birth stories on here there are a few I have read that are fantastic and very natural like.... Tracey's birth story for Zyon and also Relle's birth story for Angus. They both show how your body just takes over and you do what you have to do!!

Good luck with everything!