dog is acting abnormal

Question
My rat terrier/ min pin mix is about 6 years old. The last two days she has been acting unusual for her. She's not actively eating food but if I give her a treat she will eat it uninterestedly. She has not vomited or that I know has diarrhea. She is not playful. I did notice this morning she was eating grass which I know they do for digestion. She seems unsettled. She follows me and then will just sit and stare at me. Is this just some sort of digestion issue or could she be in pain? She doesn't seem to moan or whine at all. But she's not getting excited about things she ususually goes crazy over. Disinterested in everything.

Answer
Your dog is trying to tell you that she is sick. She might be very sick but she isn't going to whine and cry. Dogs and cats are not whiners, they know it 'attracts' predators.
So they will do what they can to get our attention and that means starting at us or peeing on the rug or pooping on the bed.
She needs to go see a vet as soon as you can get her in. She might be in pain, she might not. Small dogs generally shiver a lot when in pain or breath heavily. That is usually all you will see.
Please call the vet and get her an appointment soon.
Let me know what you find out afterward. I hope she gets well soon.