My dog is a female chihuahua, around over 10 years old (I found her on the street and don't know exact age).
For the past 4 weeks, she progressively started to shake a little as if she was cold, but it's pretty warm right now; and around 3 weeks ago, she started to eat less and sleep all day. There are no symptoms of infections such as vomiting, diarrhea or fever.
We went to the vet last Friday and apparently she has joint pain because she was licking her limbs. She got a shot of anti inflammatory and painkiller and it was like she came back to life, she looked more awake and started to behave normal again, didn't sleep all day and ate 2 times a day. The vet prescribed her tramadol and increased the dose of her artro tabs; but now, since yesterday Wednesday, she started to feel down again, even though she is still taking tramadol; she didn't eat all day and is sleeping.
I thought she could had arthritis, but just this last Tuesday she was running in the house.
My question is, am I overreacting? Is this normal for a senior dog? Could be there something else, besides pain, that is causing this?
EDIT: Updating this in case anyone experiences the same situation.
I wasn't overreacting. I went to another vet and ran blood tests, all parameters were normal; also, did x-rays. I was expecting something bad in the results or an infection so this made me even more concerned, until we did an echocardiogram and turned out to be pyometra and cysts. My guts were right to feel something was wrong; the doctor explained to me that the reason this infection didn't show up in the blood tests was because the organism can run out of these cells that indicate an infection (or something of the sort I don't remember well). She had a successful surgery and the shaking disappeared and the appetite returned.
My advice is that you should consult more than 1 vet if they say everything is okay but you feel something is wrong and keep looking and trying to find the cause, had it not been for the echocardiogram she would've probably starved herself due to the pain.