
This early on there are no outward signs to see, her abdomen won't change shape till nearer 6 weeks by then the pups are growing rapidly and can't be hidden up in the ribs any more.
Phantoms can mimic a real pregnancy, weight gain etc. right up to and including labour in some rarer cases, when I had 2 bitches who had been mated the one who turned out to be having the phantom looked more pregnant than the one who was pregnant.
It is too early to Xray as the bones of the pups have to have started to calcify to be seen, last 7 days is the best time.
If you are going to get her scanned again leave it till 39/40 days so when you are due to start her daily worming and puppy food at 42 days you will have definite Yes/No, treatment of a pregnant bitch doesn't change till then anyway.