Bunny gestation periods are around 30 days, and at 4 months old its on the young side to be mating anyway. She may just have gas, has she been acting odd in any other way?

I think what you might be seeing is normal intestine movements. It’s more noticable in some rabbits because of their fur I think. I see in in mine when he’s lying down and because his fur has different colours on the strand, it is more obvious.
Here’s a previous thread that talks about it some. (assuming this is like what you’re seeing…) https://www.binkybunny.com/FORUM/tabid/54/a…fault.aspx

From what I understand, this part of the intestine (cecum) is often most active during rest time well after the bunny has eaten.

Definitely not pregnant, she’s past the gestation. Buns digest food almost constantly, so I wonder if you were just noticing some normal gut movement or fast breathing. When my buns play, after they will breathe harder for a few minutes. One of my buns is a noticeable “swayer” too… so she is always moving slightly…

I just found a video of this intestine movement (amazing what is on youtube!)  You can see it in the centre of the picture. On the left hand side you’ll see the bunnies much faster breathing movement. http://www.youtube.com/watch

wow that vid was great! i saw this happen with Bugz the other day and wondered if something was going on but he was eating, pooing and hoping around like normal so figured he just had gas or something

That’s really an interesting video.
I would keep an eye on her poos just to make sure they’re normal in size and shape later, and that she’s eating and moving normally. If so, than it’s her regular digestion.

I am a bit concerned that your vet’s girl on the phone (med. assistant? Technician? Receptionist?) made an alarming, and totally wrong, diagnosis over the phone. You might want to let the vet know you called and that was what you were told. Doesn’t seem appropriate to me.