I've had 3 children, 2 at home in the pool. I had gas and air only.
Let me start by saying I hate pain so much that I've never even had my ears pierced!
It's honestly fine. Watch lots of positive birth videos where people just 'breathe' the baby out and you'll see how it's meant to happen. I didn't push at all, except once or twice at the end when my body told me too.
A contraction only lasts for a minute or so (less at the start), and even then it's not a minute of pure pressure. It builds up to a peak within that minute, and then comes back down to nothing within that minute. And also, between contractions you rest and feel normal.
I couldn't understand (every time) how an opening so small can fit a baby through, yet it is designed to do exactly that.
Breathe the gas and air in as deeply as you can as soon as you feel the contraction start, as it takes 10 seconds or so to hit you - enjoy the tipsy feeling.
Breathe deeply and with an open mouth.
My top tipis to never watch trash like One Born Every Minute! Watch positive birth vids on YouTube. Makes you realise how wonderful birth is - something to be excited about, not something to dread.
Enjoy :-)