Constipated Momma-to-be?

So, as you know from my previous thread, I brought in a stray pregnant cat. She's been going to the litter box the past few days and has only been straining and hasn't been producing anything. I told the vet yesterday that she was seemingly constipated, but the vet didn't seemed concerned, however, I am.

She meowed a few times today (which is unusual because she only tells my other cat to stop bothering her and he was nowhere near her), but is mostly laying on the floor. Is this normal? I don't think it's labor yet because she hasn't leaked any milk and her vagina seems dry.

Hopefully one of the more experienced members will be along to advise you better than me.

What I know from my experience is that a pregnant's mum's elimination habits before labour do go quite funny. Ive experienced the opposite...more liquidy poop, as opposed to constipation.

Is she getting enough water? Is she eating well?

when lilly was pregnant about a week before she was due she had constipation quite bad with blood in it , i was worried so i took her to the vet who put her on to a special royal canin diet for sentive stomachs , i cant remember the excate name for it but it did help her.
maybe phone a different vet to get some advice? but also like minxie said sometimes before they go in to labour there *habbits* can change either way.