Hello everyone!

I am 27 weeks pregnant on Monday.. First ultrasound was at 14 weeks and 2 was 15 3 was 20 weeks and I think MY doctor gives another at 28 but I don't want to stay with this doctor anymore.. My mother picked her for me.. And I've wanted to go to a birthing center (insurance covers it)

What week of my pregnancy should I call the birthing center.. Will they still take me? I just want a natural birth not a water birth if that makes a difference ..