Could my rabbit be pregnant?

My rabbit is normally a calm placid female, who came from a litter that we bred ourselves. In the litter, there was 4 bunnies, 2 males, and 2 females. One of the females, being my rabbit now. They are now about 15 weeks old. We gave away one female, and one male, and were left with one female, my bunny, and one male. They were living with each other, until obviously, we had to seperate them. We split them into different hutches when they were exactly 10 weeks old. Now, my rabbit's belly is very hard, I saw movement and wiggling in her belly, lately she has been very frightened and wide-eyed, and she has grunted at me 6 times in the space of 20 minutes. I already know that the normal gestation period for a bunny is up to 35 days, but I'm sure she would be around 40 days. Is there a chance she could be pregnant?