If she's a month along (1/2 way thru) she will only just be starting to show now.
I don't give any additives to the diet, that's my preference. I do however around now start to introduce her to puppy food as its higher in vits, minerals etc, my expectant mums stay on this now until the puppies are starting to wean.
You also need to consider worming.
About two weeks out from their due date I get the whelping box prepared and start having mum sleep there of a night. It should be a quiet room away from traffic and the other dogs for the first couple of weeks.
Neither an X-ray or ultrasound are 100% accurate as to number of pups to expect. If you are going to get an X-ray done wait until later for the bones to form more.
My Kelpies never suffered from morning sickness or tiredness nor did they refuse food or vomit on the day of whelping but my Whippet bitch showed all the classic signs.