Have you had a "troubled" pet? Will you share your experience with me?

I currently have a troubled cat that is causing some real issues in my life…I’m sure I’ve asked a thousand questions about him on here before, but here’s one more. So if you’ve had a pet that was hard to deal with, how did you handle it? How did it affect your life? How bad did it get? And did it ever improve?

This question was originally much longer but I decided to shorten it because the details are not what I’m asking about. To provide a tiny back story though I have a cat with health problems who is being treated for those health problems but other the course of the past year (since he began treatment) things have not really improved. He has always been loud, and frequently pooped outside of his litter box, and vomited a lot. I was told with his new medication (he was found to be hyper-thyroid – a giant relief to me since it explains his symptoms and is treatable) all these things should be diminished greatly. They haven’t. He still screams and screams, poops all over the place for no reason, and vomits constantly. Sometimes more than once a day. Sometimes it is just whole food that he has clearly not chewed and only a few bites of it so it’s not like he’s overeating. To top it off this whole situation has caused a bit of strife lately between my boyfriend and I who thinks I am overly sensitive about my cat. We live together, and have another cat who is completely normal, and he just doesn’t understand what it is like to have a cat that isn’t normal. I’ve spent a lot of money, as much as I’m able to, on him up to this point, and I don’t know what else to do. It is really difficult, and it’s on my mind all the time. I never stop worrying about him.

Any similar experiences, please share. I feel like I need a support group, even though I also feel like thats ridiculous.