Size of pregnant cats

Is there a average size pregnant cats should be within there last week. I am worried that my kitten isn't big enough. I brought her to the vet Aug 6th and was told 3-4 weeks left and he counted two kittens. She doesn't seem that big though, she is alot bigger than she was. She is a tiny cat, is only a year old and was tiny when I got her. Should I be worried? She had a little bit of bloody discharge last week. She is meowing more than usually but its not a worrying type of meow, its just when I pet her or when she wants me to pet her. She is sleeping alot, mostly in my bed and her nest.

Here is the most recent one I have of her, the basket is her nest, she has now pulled the towels out of it so its just the sheet in there.

Oh and one thing different that she has started to do recently is lie down weird. She'll lie down with her front paws forward and head up and back legs spread out and flat on the ground. It just seemed weird to me because she never lied like that before.

I took this picture today, but like this:

I don't think there is any standard. It's like people, some "show" more than others. Will she let you measure her around the middle? If so, you could keep track of how much she is actually growing.

How sure of the dates are you? When I took Goldy to the vet he said 2-1/2 to 3 weeks left. It turned out to be 4-1/2 weeks! She was a stray so I didn't know the exact date she got pregnant. Anyway, she never looked big enough to me until the last week all of sudden she blossomed. Still not huge, but she delivered three healthy babies.

Goldy also did the thing lying with her back legs spread. I thought she was trying to make more room for her belly to spread out.

This is my only experience with a pregnant cat. Someone else may have more ideas about what's going on with your kitty.

I am not exactly sure of the dates :S I wish I knew more for sure. I could try to measure her but sometimes she is very picky about being touched.

I know she was in heat about 65 days ago and took her out of the house for a few days because the male cat was there, not sure if he got to her then or after