I expect to give birth in less than a week, בשעה טובה. It is very important to me that the doula be with me for as much time as possible- I hired her to be there to keep me calm and if, by chance, there is a Kohen warning outside of the hospital at the time when I need to go in. My husband is a Kohen.
I have hired a doula who said that she will answer her phone on Shabbat/Yom Tov. The question is can we call her and, if so, at what point can we call and how often.
Answer:
When it is clear that labor has begun or is imminent, you may call the doula to assist you and accompany you to the birth.
See Shulchan Aruch 330:1-2 and Mishna Brura ibid.