Vicky,
Don't cry.... I wish I could say something to ease your pain... you have our love and support and hugs.
As for Rocky's panting... Ginger did that too. Though they are different types of cancer, Ginger panted a LOT. I have a paper in my Jeep where I wrote down Dexters rate of breathing versus Ginger's rate of breathing... and let me tell you the difference was very BIG. It scared me, that's why I wrote it down.... When they were both laying on the couch, resting, I got out my watch and counted. Dexter breathed in maybe 20 times a minute, while Ginger breathed in maybe 90 or 100 times a minute (at times I couldn't even count them) -- while RESTING. I think hers was partly because of her medicine, but also because she was just tired. Getting around on 3 legs is pretty demanding, and battling cancer is pretty demanding.
Don't panic... it was pretty "normal" for Ginger to pant often. It's scary, I know, and like I said they are different cancers, so maybe someone else has more advice. I wish I had more to say.... and better advice.
Vicky, you have our prayers and thoughts... I wish I could do more....