Your situation describes my cat perfectly. Always a bouncy ,playful kitty (she is 4 years old and in/was in good health). She was so lethargic,(began all of a sudden) that I took her to the vet three days ago. She needed an enema.They did x-rays first(all good) ,and blood work (all good). They gave her a shot for nausea and for hydrated her.Brought her home and after an evening of still having bowel movements,poor little thing finally slept. Yesterday,still lethargic,with slight improvement. Same today. She is ,thankfully ,eating. But still not her old self. She is up to date on shots and gets Revolution monthly.NEVER goes outside. This is NOT my Lulu. Very concerned. Do not kow what else to do. Have spent almost 900.00 on her this week. Out of funds.Really do not know what else to do for her. (Forgot to mention.She is on Purina Pro Plan for hairball control. Has been on that for over two years. She is longhair and gets brushed regularly,to keep hairballs at a minimum)