My girl had her pups on Friday/Saturday.

She has been perfect since, she is eating, she’s alert, tending to pups and still wanting to be social with our other dogs on her terms.

I’ve noticed though her back end is sagging, when she squats down for a wee her vulva is touching the floor.

Anyone know what if this normal or if not what it could be?

What breed is she? Is it a breed suseptible to spinal issues?
Is she OK walking, climbing steps etc?

I don't think I understand what the problem is from that description.  Is it her actual legs that can't hold up her body weight?  Or are you saying that her uterus/vulva has prolapsed or is hanging down??

She is a German shepherd, sorry I thought I had given more details, in a little sleep deprived at the moment with the puppies and mum.

She is fine, running and jumping like she always has, its more a sag between the anus and the vulva.

It's normal for a newly-whelped bitch to be saggy behind; it takes a while for the muscles to tighten up again. But if you're worried, ask your vet. Good luck!

It doesn't sound quite normal to me.  I think maybe you can take a photo and a video of it, and email it to your vet to ask if they want to see you - that will avoid you having to make a trip in unnecessarily if you're not sure.