I have a 5yr old female GSD she had her season over 3 wks ago. Near to the end of her season she became depressed & lethargic However, she was eating her meals just fine.
I took her to the Vets, her temperature was slightly high, they put her on antibiotics & Anti- inflammatory, they seemed to do the job for the 1st 2 days, but she went down hill again ( depressed & lethargic) walking with her head down, can’t seem to turn her head, turning it like she has a stiff neck????
So, back to the vets, she had a blood test done, which showed she has high white blood cells, indicating infection somewhere? Vet changed her antibiotics to a higher dose… Still no joy!
She can be ok one day, then back to what I described the next day.

She’s been back to Vets again, had a scan.. vet says it showed she had a slight swollen tube to her uterus (Closed pyometra ) was mentioned, but, she didn’t have any of the other signs (Drinking lots, vomiting, discharge) she’s eating pretty normal

Vet advised to try the injections they use to terminate an unwanted pregnancy in a bitch, saying it would help to clear out anything untoward in her uterus, I went along with this, as you do, thinking vet knows best!!! Still, had to take her back this week she still has a high white blood cell count & slight temperature, so more antibiotics prescribed and still she’s up and down!!!
It’s driving me nuts as to what’s wrong with her????????????????????
The vets don’t seem to have a clue!!!!

You need to get some more opinions!!! ASAP. Keep a close on her temp until you can get to a different vet

In my opinion, my best guess, an internet diagnosis, ridiculous, is that this dog has a pyometra and should be spayed ASAP.
This common condition can be life threatening if it is not treated. The womb essentially becomes an abcess, and the treatment for an abcess is drainage (surgery), not antibiotics.
Most drink tons of water, pee a ton (PU/PD), and vomit. But not all. I'm thinking the Rx given has held the infection in check, but hasn't cured it.
Just a GUESS. Also, the temperature can be below normal in pyometra.