My cat is also 3.5 years old. He vomited a week ago. This never happens. He has been staying in our bed and not acting himself. His appetite is seriously suppressed and he is drinking less water.
He is indoor/outdoor. He has been using the litterbox for the first time in 1.5 yrs so atleast we can see that he is peeing OK. His blood work was normal for CBC, renal, gucose, thyroid. He is 13 lbs. He has had 2 visits to the vet in 6 days. They can't find anything wrong. My husband said he saw Dash lying down in the litter box today - very odd. Not laying on his side but laying on his belly. He is not making any noises and is not distressed when picked up or handled. Such an abrupt change in his manner for such a young cat. We have not used any flea/tick ointments and he has not had a flea collar much in the past 8 months.
He did have a few ticks in his neck area in Sept, October. He was losing his flea collar constantly so we gave up. The vet thus far has not expressed concern over exposure to ticks or racoons.
I'll let you know how this works out. Let me know how your cat is doing.