My 13 year old cat has recently begun to lose weight and she has become increasingly lethargic.?

In the past two weeks she was started to sleep for 15-20 hours a day, and she has lost around 2 pounds. She still eats about the same, maybe a little less but she doesn't appear to have any trouble eating her food, no tooth or gum problems. In the past she has become extremely agitated while visiting the vet so I'm not quick to take her there in her elderly state. I love her dearly and just want to make sure she is comfortable while I have her with me. Is there anything you can suggest that I can do to make sure she is the happy kitty I love?