PBE, I so understand where you're coming from. This has brought up a lot of memories for me. I got pg by my 2nd dh when my dd was 9 yrs old. I had a horrible birth first time round, they refused to give me spinal block when I was in active labour and it went on for days. In the end I had ventouse with bad and painful cuts. Not half as bad as what you went through but I was very traumatised by it. I then went on to have really horrendous PND although looking back, I wonder whether I was suffering from PTSD instead.
Anyway, when I got pg with my 2nd, I had a nervous breakdown and spent about 4 months of pregnancy in a terrible anxious state and was utterly terrified of the impending birth and the thought that I was told I would probably have PND again. I was in a terrible state and I confess that I didn't want to have the baby at that point.
However, my point is that you are unlikely to have the same awful birth experience again. I had an OK birth in the end and did things differently. I did have PND again but the HV was looking out for me and it was very short lived and treated immediately and so wasn't the big prob I thought it was going to be. I often think if only I'd known that it was going to be OK, I wouldn't have felt so bad when I was pg.
There are things you can do to ensure that history isn't repeated. Forewarned is forearmed and you can choose the birth you want, ie C section.
Hindsight is a great thing but I so understand how you feel because actually, words like those above don't help much because of the terror you're feeling. But believe me, if you decide to go ahead with the pregnancy - and this is absolutely your choice - your experience will almost likely not be anything like as bad as your first one because you will be in control and will have made provision. In the end, all this stuff will be a distant memory I promise you.
I so feel for you - it's a horrible place to be.