Hi Amanda
What you are describing suggests that she is due to kitten quite soon….but that can mean up to 2-3 days yet. these final signs can linger a while. It’s impossible to be sure. But the fact that the kittens are moving down probably suggests sooner. Presumably you don’t know the date she mated. The normal gestation period (pregnancy) for cats is 63 days, plus or minus a few days. I’ll go through the whole process of birthing so you know what to expect and what to watch for.
As the time approaches you will notice the restless behaviour you’ve mentioned and sometimes the cat will withdraw a little, seeking hiding spots or exhibiting nesting behaviour. It is important to understand that there is a separate labour for each kitten. Between each kitten's birth there will be a "rest period". This can be as short as just a minute or two or as long as an hour or so. So the time to have all the kittens can vary considerably and is not so important as the time for each individual kitten's birth. When labour is imminent she will lie on her side, perhaps glancing to her rear end and shifting herself as though trying to get comfortable. Often there will be some panting. Then labour commences with abdominal contractions. Once these contractions commence a kitten should appear within a few minutes. If she is straining for more than a half an hour or you see a part of the kitten appear at the vulva but not exiting quickly you should contact a vet. The kitten may be born packaged within the membranes or sometimes not. The mother will usually clean off the membranes and eat them. She will chew the umbilical cord and eat the placenta. If she seems not to be managing this process you can assist by breaking the membranes open and breaking the cord (just use your fingers). Allow the kitten to find her teat, assist it if you need too. Don’t take the kittens away from the mother, she may get quite upset. So after the first kitten, as I said, there will be a rest period. Then labour will commence for the next kitten and so the process continues until all kittens have been born. Between each kitten the mother may not seem fully relaxed. After the last kitten she will settle down and seem much less anxious....that is how you will know she is finished. If you suspect there is more kittens to come and nothing has happened within 2 hours then you should contact a vet. If you are sure of the day she mated, then count 63 days from that day. If she has done nothing by day 64 get a vet to check all is okay. And once she has finished kittening you should take mother and kittens into your vet to check all is okay and discuss kitten management.
The following site is a veterinary information site on female reproduction
http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=1738
I hope I’ve been of help. Good luck.
Regards, XXXXX
Cat Veterinarian
Bachelor of Veterinary Science University of Melbourne