I have had a similar experience. We started with injections, which were very difficult, and switched to pills eventually. It was a difficult and expensive process, but totally worth it. My cat was very nearly dead, and now he is healthier than ever. You would never know he was sick.

I went through the FIP Warriors 5.0 Facebook group. They are legit, and they do much more than help you find the medicine. They support you through the whole process.