
How about finding a canine Osteopath in your area and seeing if she could be seen as an emergency? I had a 3 week old pup who was screaming in pain whenever another pup much as looked at him. The vet told me it was a trapped nerve and gave him a steroid injection. It got worse and poor pup was in so much pain I was in tears as I couldn't bear to see him like it and felt helpless as I couldn't even comfort him as any interaction sent him into a screaming fit and he would fall on his side with all 4 legs out stiff and would lay like that screaming for 30 - 40 seconds. I phoned an osteopath who had helped one of my gundogs and she saw him. It turned out it wasn't a trapped nerve at all, turned out it was a joint sprain with capsulitis. He was treated over 3-4 weeks and although he had to be isolated he is now a very fit and healthy 11 month old with no problems at all. It is amazing what they can feel and what they can do. With my gundog she was reluctant to swim, jump and then went lame, the vet wanted to do full x-rays strait up but I insisted on seeing the Osteopath, turned out she had tight Hamstrings, 2 treatments and 3 years later at the age of 12 she is still doing a full days work!
Hope all goes well with your girl if she is in Whelp, at 43 days the vet should have seen pups but it depends on how experienced she is at scanning and sometimes a small litter can hide.