Congrats on #4!! I'm no expert but also attempted a VBA2C like you with my last birth (although didn't go to plan.....). I would maybe take a look at all the reasons why your VBA2C worked. What support did you have? What education did you arm yourself with? Can you hook up with your midwives again and start the process now of mental preparation. What sort of exercise regime did you do to prepare for the birth? (it's a marathon event after all!)

You know as much as anyone how much is involved in a VBAC. Giving birth naturally last time was not a 'fluke' - you worked really hard to achieve it and you had all the stars aligned! A counsellor may help or an independent midwife who understands and has supported VBACs and can help you prepare for the challenge. Gain confidence that your body has birthed a baby naturally and so it can again.