Need advise on sick cat

I have a 3.5 year old cat... about 5 days ago he stopped eating and has been hiding, not being his normal self. Took him to the vet, treated it like it was a bacterial infection. He ate fine for a day, but now back to not eating and hiding. Vet did blood work today and said his numbers were low, but platelets were really low. Rattled off a couple of things it might be, which all baffle me, as he is in indoor cat.

Anyone ever had anything like this with one your your cats? If so, what was diagnosis and did it cost a lot to help him get better?

So your cat is anaemic? What did the vet give you? Can you give us some detail about what the vet said? 

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.

Can you tell me what you are feeding him?

You haven't seen him defecate?

Personally I'd either get the vet on the phone and explain that he isn't bouncing back or take the results and get a second opinion. 

I hope that the symptoms sound familiar to someone and that they will be able to help you.