I have a 13 year old Westie, Maggie, and she is sick. She is an incredibly healthy dog and until this point I have never had to take care of a sick animal.
I have noticed subtle changes and thought they just had to do with being a senior dog.
However, today when I got home from work I noticed an array of problems. She has little appetite. She has not eaten any of her own dog food so I tried steamed rice, eggs, and chicken. The only thing she ate was a little bit of chicken. Also, she is having problems defecating. She is constipated, but when I took her outside to go potty she had diarrea. She has been shivering mush like a human with a cold. She got cold so I wrapped her in a heating blanket and she seems better. And the most alarming problem is that when I first got home I was petting her and she uncontrollably urinated on the couch. Now this is not the first time that that has happened. A few months ago she accidentally peed on the bed while sleeping so I just made sure to take her out more often to go potty. The urinating problem seemed to go away until today.
I'm not sure if she needs to see a vet right away or of it can wait. I already called the vet and told them the symptoms. They said that the earliest appointment would be Tuesday (4 days away). Is that soon enough? Please help!
Thank you.

That is totally going to be a personal judgement call, now if I was the one in the situation I would be taking her to the ER Vet, no questions asked. She has so many different things going on and being that she is older there could be more than what you see. Good luck

Seems that your Westie has got some virus... :(

Any older dog should be taken to the vet immediately if showing signs of illness.