When my grandma found a pregnant stray she seemed to be in "active labor" for about 2 days. Just seemed in distress , paced around, plopping her bottom on the floor, panting. Then at the end of day two she let out a howl and one was coming out. We very gently moved her to the box which was only a foot or two away and she gave birth to 5 kittens in about an hour and a half. Not sure if all that is normal but that's what happened to me and my grandma a few years ago. Hope everything goes smoothly :-)