Worried about my cat

My cat's health has taken a turn for the worse this week and I'm really worried.  I guess that I just wanted to get other opinions and reassurance.

Last Sunday my cat started vomiting a lot and looked like she was feeling miserable, she couldn't hold any food or liquid.  I took her to the vet the next day, and her liver enzyme levels were high so he recommended that I stop giving her the medication she was taking (for hyperthyroidism) and see if she got better.  Fast forward to today, she looks like she's feeling a lot better and she is more active and acting more like her usual self.  But what concerns me (sorry for being gross lol) is that she hasn't pooped since like Sunday.  She is running to the litter box frequently and trying her best to go, but nothing is coming out.  I took her to the vet again today and mentioned this but he didn't seem to think it was a cause for concern and said her digestive system was still probably playing catch-up from her vomiting episode.  He also felt her colon and said it didn't feel full.  She also just threw up again a few minutes ago so that has me even more worried!

I'm just not sure what I should do, if anything.  Going to the vet so much is expensive, and so far he hasn't done anything other than to tell me "keep waiting and see if she gets better".  I may just be overreacting since this is the first time my cat has been really sick, but I'm really worried about her.  She is getting old too, she's around 16 or 17 now.

Sorry your cat is feeling poorly.

You could try adding a teaspoon of plain pumpkin (not pumpkin pie filing) to her (hopefully) wet food. 

Is she urinating okay--any change?  The reason I ask is because the very first time Ritz went in/out/in/out of the litter box I thought she was constipated, as did the vet.  Turns out she was developing a UTI.

I would call the vet back and tell him/her she hasn't pooped for six days and what does he suggest.

Sure hope your cat is doing better and has pooped and quit vomiting. Please post an update if you can. You are definitely not overreacting. She's running to the litter box for some reason. Could certainly be a UTI as @Ritz  mentioned. The stance for peeing & pooping is subtly different, so if you observe her straining in the litter box you may be able to determine which is giving her the problem. Is she still eating & drinking? 

When I had not seen Simon poop when this started the vet  me to give my cat some canned pumpkin.....that it can help them poop easier.  Worth a shot and pretty cheap.