I would second ib's advice and try to see some positive births on youtube or similar. It is totally natural to be fearful of the unknown, but you will probably find that when the time comes you will, if not enjoy it, at least get through it. Just try to remind yourself that your body is designed to do this thing. Try not to worry so much about after the birth (stitches, etc...), as you will have your gorgeous, wonderful new baby who will occupy your every waking moment!
Talking to your Mum may actually be a help, as she will have loads of experiance, and might be able to talk to you about the things you are scared of. Knowledge is a great thing when it comes to getting rid of or lessening fear IME.
I have no experience of a water birth, and was not planning on having any pain relief other than gas and air. When it came to it and DS got himself stuck (prob not what you want to hear, but it does happen, and the MWs are very good in these situations - mine was very calm about everything, and never once said anything to worry or panic me, just very reassuring), I had to have an epidural so that they could use forceps (with a view to CS if not successful), and it was instant and very welcome relief. I had no problems re the epidural at all, even though, like you, I didn't plan on having one or really want one.
Just try to be positive and address your fear now while you have time to do something about it. Try not to worry about the 'what ifs'. Good luck! 