My dog 🐕 I'm worried

I'm pretty worried 

My dog, a 10 year old medium sized female

She hasn't wanted to eat for days, she is down and her nose is dry...I don't know what she could have, she ate a little of my cat's food that she loves to eat because she is naughty and gluttonous. 

But she has not wanted to touch her food and has not been attracted by the aromas that she has always loved most.

I'm worried, could her tummy hurt?

Or maybe a tumor?

Or maybe cancer?

Maybe she's about to cross the bridge..

I know sooner or later it will happen but I'm afraid of those possibilities.

:"(