I don't know much about this but in a cat book that I have it says that although 65 days is often quoted as the average length of pregnancy in a cat, you should not be alarmed if labor starts as early as the 61st day after mating or as late as the 70th.

Development of the unborn kittens begins in earnest 16 days after fertilizaton. At 18 days the yolk sac is shrinking and an embryonic backbone is developing. Four days later the embryo is receiving life support from it's mother via the completed placenta, and it's limbs, head, and eyes are forming. Four weeks after fertilization a miniature kitten about 2.5cm(1in) long
with all it's organs has developed and from now on it's known as a foetus. The foetus grows rapidly and at 5 to 6 weeks it's about 6cm (2 1/2in) long. This doubles by 9 weeks just before the kitten is born.

The book doesn't say anything about the kittens being active or moving around. Maybe your cat is much further along than you think. If her nipples have become quite pink and the surrounding hair recedes slightly, it's a sign that the kittens should arrive in about 6 weeks. I hope that both mother and kittens will continue to do well. Will you spay her when the kittens are weaned? Do you have any prospective homes for the kittens? I hope so and good luck.