Bitch pregnant with singleton, Have some questions from a worried sick momma

[GSDMaciemoo]

My female GSD is pregnant and due next week the 21st with a singleton. We have had 3 ultra sounds and 1 x ray and were sure shes only having one. My vet told me with one puppy she may not produce enough horomones to go into labor but then told me he wont do a c section unless shes in active labor, well what if she doesnt go into labor at all. Im so worried I dont want to lose her or the puppy. Does anyone on here have experience with a bitch giving birth to a singleton? If so could you please tell me what your experience was like. I need some reasurrance that other dogs have had a natural delivery with just one so I can hope she will.