I'm so sorry to read your sad news.
I lost my GSD X 4 years ago to Lymphoma.
Like you, I took her to a vet, because she "just wasn't right" the vet checked her out and put her on an arthritis treatment (she was 12).
About 3 weeks later she still wasn't right and seemed to have a sore throat, so I took her to another vet that I had a lot of confidence in he diagnosed her with lymphoma and suggested that it was probably too far advanced to treat effectively. We put her on a cortisone treatment which picked her up for a couple of days, I had about another week with her, which I'm very grateful gave me time to do all the things she loved one last time. Before she went to the Rainbow Bridge on a lovely spring afternoon.
Good luck, my thoughts are with you.
