Hi my cat seemed to go off her food and just seem unwell, so i took her to the vets, and they told me she had back pain and needed her teeth cleaning, so they checked her blood as she is 13, and cleaned her teeth, and was put on metacam for 7 days, she seemed to be fine eating well and happy, but drinking a lot. When i stopped giving her metacam, again she started to look lethargic and go off her food, so i gave her some more metam last night, but this morning she dosnt seem to be able to walk, is rapid breathing and has vomited some white froth, she lies flat out on her side. What do you think has happened to her?