[bazzais]

Dont make too rash a judgement on your vet unless needed, it sometimes the same experience for them as you.

Its nt an axact 'science'. - its biology.

Thats said - all said - i hope she recovers and lives on.

[Marches Farmer]

She may have internal damage which is affecting her bladder.  If you have a new vet and want to keep the ewe then she may need to be checked out.  I cull hard and would seriously consider doing so in this case.

[bj_cardiff]

I think if she was mine I'd wean the lambs early and cull the ewe. It sounds like she's in discomfort or pain and you must of already spent quite a bit of money on her.

[landroverroy]

 I would definitely consider cystitis as she's been doing well for 8 weeks. I had a cow with it and it was rapidly cured with a homeopathic remedy from Crossgates Homeopathics.
However cider vinegar or bicarbonate of soda are also effective to relieve the irritation as they alter the acidity of the urine.
Or you could ask the vet for some antibiotics. You should be able to get these without a visit as the vet has already seen the animal recently - keeps the cost down.