If you don't want to be a burden then run along like a good girl and let them do a section? NO! I don't think so!

Your Doula is a Doula because she wants to empower and enable women to have the births they desire and deserve, YOU ARE NOT A BURDEN! I assume you are paying her for her services, and that part of her services are "labour and birth support". Now, neither of you are in control of how long your labour will be, so it is common sense that there's not a "right" time to call her in terms of time, only in terms of when you need her.

Having read a bit about what you went through last time and what you are going through now in your decision-making, i think you ought to call her as soon as you want her. My birth support woman (a friend not a doula) came when i was still able to chat through contractions and i really felt like we'd got into a groove before labour "got going" hard and everything just seemed to flow really nicely. Good birth support makes birth safer - you know this yourself, that's why you chose a Doula to care for you. Bearing in mind that you are having her help because it is safer, it makes no sense to try not to call her until it's "real" or "heavy" or whatever. If i had waited until i was desperate before getting DP to sit with me i would have been unable to do so, kwim? THings can get heavy fast.

You make an excellent decision in employing the doula. Call her when you want her and let her do her job.

Wishing you a WONDERFUL birth, you really deserve it.

Bx