"I couldn't believe it. I was going away, somewhere far from my master.
My ears flapped weakly as I stood upon my hind legs, whimpering sadly. My brow furrowed weakly and my eyes watered as I looked upon my master."
Here, you refer to your master twice, which is perfectly fine, but it does sound repetitive. Perhaps replace the word with a synonym or simply use "him" or something like it? Just a suggestion.
I'd also like to suggest another way to express the dog's feelings towards the previous owner and the new. Why not describe the eyes of both humans, using positive description and attachment towards the view of "master's" eyes and using negative and assuming coldness towards the stranger?
Using representational comparisons in situations like these can really add to the emotion of a piece.
Overall, I absolutely love the sad tone and the questioning lack of understanding. I hope you add more to this, I enjoyed reading it. Good work!