[luckylady]

One of my females had a singleton pregnancy. I think what you are feeling.....or not feeling, is fairly normal for a single puppy.
I had an ultrasound done early to confirm pregnancy; even with that conformation of "yes she was pregnant", I was doubting it practically til the day she delivered!! Only carrying one puppy, she didn't get really big, so I kept going back & forth..."is she, or isn't she?" Then the x-ray day came and I saw the skeleton on the x-ray with my own eyes and heard my vet say "she's got one very large puppy" (which scared the living daylights out of me). But even with that, there must not have been a whole lot of movement, and I swear I still wondered, even if just a tiny bit to the very end.
Long story short, yes there was one large puppy....just shy of 7 oz. Thankfully my 6 1/2 lb girl whelped him naturally.
After the fact, I would guess that with there being only one pup, movements might seem fewer & far between because the pup has more room to stretch out. Because there are only four little paws & one head in there instead of 8, 12, or more moving around, seems logical that, less paws + more room, would make movement less noticeable.
Wishing you good luck with your girl; let us know how it goes.