I am sorry to read your post. I know from experience how upsetting it can be to really want something but be too afraid to go after your dreams. I do not have any personal experience of ME but I know of people who have had the illness and gone on to have families. Yes, they have had to put support in place, during their pregnancy and once the bubba arrives but they continue to thrive and be great mums. With the right support could this be you?
I am currently pregnant (36 weeks today!) and had similar fears over childbirth. I completed a hypnobirthing course some months back and feel completely different about birth now. It has given me and my OH many different techniques to help with fear and anxiety in life, as well as birth. Obviously I have not had my baby yet but I am so much more confident about the while birth process because of it and no longer have fear of it. Our bodies have been built for it after all.
In terms of pregnancy, I'll be honest, it can be hard. At times you may feel rough, at other times fantastic. Different women feel different things at different times. I have never felt in pain though, maybe some discomfort but certainly not pain. Focussing on getting the nursery ready takes your mind off these things anyway. I am an older mum having her first baby and thought I would really struggle with pregnancy but would say on the whole, I have really enjoyed the experience to the point that I would do it again. I am sure you will find other ladies on this site with a similar viewpoint. It's not all bad and 9 months goes very quickly!
Finally, with regards to postnatal depression, please don't assume that because you have had depression in the past that you are at a higher risk of getting postnatal depression in the future. The NCT (national childbirth trust) has some interesting stats on this. They have found that women who have suffered with depression ( I am one of them) in the past have been helped considerably by the birth of their baby. Quite simply because the focus is no longer on the self but instead on the baby.
I really hope you can resolve your concerns. When I was in a similar boat I found that sharing my concerns with my close friends was very helpful. They had children and reminded me of how well I got on with them and the joy that they give which far outweighs the fears. 18 months later and I am now very much looking forward to the birth of my first child.
I wish you all the best and hope that with sharing your fears with those closest to you that you can overcome your fears and go after your dreams.