I went through a similar experience with my last (second birth). I had been told I’d had a second degree tear with my first but I had two bouts of bowel incontinence in the subsequent 3 years and after seeing a specialist perineal care midwife she said it had probably been a third degree tear.
She examined me and gave me some tips to birth naturally but warned it was almost certain I would tear again.
I booked in for a caesarean but even after hypnotherapy was too scared to go ahead with it.
I decided to go for a vaginal birth.
This was the advice she gave me which I put on my birth plan.
Second Stage:
It is a priority for me to minimize perineal trauma.
I would like to deliver on my left lateral.
I would like a warm compress on my perineum during second stage.
I would like a “hands on” delivery of the head and shoulders by an experienced midwife.
I would like to pant out the head.
I would like to use spontaneous pushing.
If an episiotomy is required, please adopt a wider angle >60 degrees.
I would like a SLOW delivery.
The birth went really well. I laboured in water and delivered on land (apparently water is worse for tearing). I had someone hold my right leg up and the midwife kept a compress on my perineum. The slow delivery was more intense than the speedy standing delivery I had with my first (which caused the tear!).
I had a second degree tear but this healed quickly and caused me no further problems.
I haven’t had any incontinence since.
It’s a really tough decision. It sounds as though your incontinence issues are maybe a bit worse than mine were. The problem is that the doctors can’t promise you anything with a vaginal birth, whereas they can control the c-section for you.
Best of luck, it’s not an easy but I’m sure you’ll make the right decision for you.