Young cat illness?

Question
My cat will be 3 years old in October and she weighs about 5 lbs.  In the past week I have noticed a big decrease in her appetite and thirst along with decreased stools.  Her regular habits, like greeting me at the door when I come home, have changed.  She just lays on the couch and once I sit down, she is immediatly on my lap.  My schedule has changed and I am away from home for 12 hours as opposed to 8 hours.  Her obsessive cleaning has also decreased.  A vet a couple weeks ago said that she could have anxiety due to her obsessive washing.  She washed so much that she wore away a lot of her hair on the back of her tial and legs.  She does not physically look or seem in pain.  Any advice or information that you have would help out a great deal.  I do not want to stress her out by taking her to the vet office if there does not seem any reason to do so.  I am really concerned about her.  Thank you very much.  

Answer
A 3 year old cat that weighs 5 lbs is either unthrifty or very small.  Lethargy in cats may indicate fever.  Hair pulling is usually related to the skin itching, rather than behavioral problems. She probably needs to be checked out again by the vet and possibly have some blood tests. If they are OK, then I would treate her for the itchiness first.