A normal pregnancy lasts for 58 to 71 days. A pregnancy that lasts for longer than 71 days is usually not normal and an ultrasound should be done.

It's normal not being able to feel the kittens very close to the delivery since the kittens are all lining upp in the two uterine horns.

If you can't stay at home watching her, give her a separate room. The delivery itself is very stressful for mum and the other cats can make it worse. Make a nice and warm bed for her in her own quiet room.