Cat won't eat; first visit to vet was not helpful
One of my cats has stopped eating. She ate very little on Sunday, and nothing at all on Monday.
I took her to the vet on Tuesday morning. He gave her some fluids, and also an injection to stimulate her appetite. On Tuesday evening, she eat a tiny bit of wet food. Since the vet visit, and until now, she has at least been drinking water.
However, she has gone back to not eating at all.
She sleeps for almost 24 hours a day. Sometimes she will sit up and in the same place for 30 minutes or more with her eyes closed like she is drowsy and falling asleep whilst sitting up. This is behaviour that she never did while she was healthy.
She never plays since becoming ill.
Since she has become ill, I have occasionally heard her take strong a noticeable breaths, as if she had trouble breathing. I told that to the vet on Tuesday, and he dismissed it as not a serious issue. He said something about checking her mouth to see if she gets air, but he talked too fast, so that I couldn't follow exactly what he said.
I think she may have a lung issue but the vet is being too dismissive of that possibility? What do you think?
The vet told me on Tuesday that if she does not get better, I'll have to bring her in again and have blood work done on her.
Is blood work the best way to determine what the problem is?
I do not have an unlimited amount of money, hence I am trying to minimize the costs of vet treatment. I'd prefer not to pay for blood work if after the blood work is done, the vet is going to say: "her blood is normal." That's what happened the last time the vet did blood work on her due to another illness; I wasted ~$250 on that blood work. I don't have piles of $250s to throw around like they are water.
Don't get me wrong, I am willing to pay to get my cat better. I just want to make sure the services I'm paying for are absolutely necessary and helpful towards solving the problem, and hopefully not to bankrupt myself in the process of paying to get her better.
My cats are both indoor cats, and never go outside, ever.
She 100% does not have FIV, because both the breeder and my vet tested her for that previously (which is part of what wasted my $250 last time), and she has never been exposed to any way of getting that.
Can you guys please advise me:
1. What do you think the possible causes might be for my cat having stopped eating?
2. What are the possible solutions to this problem?
3. Is blood work the best way to identify and solve the problem, or are there better tests instead? I.e. would blood work determine if it's a worm or lung problem with my cat?
4. What should I advise my vet to do in order so that I can minimize my costs in getting this problem fixed?