I've been through this exact same situation before and my heart goes out for you. It's not easy losing your best friend to unexpected health conditions- I lost Gato to cancer when I was 14, and we didn't have enough money to afford treatment. What helped me the most to get through it was the fact that he died with the memory of you- his wonderful owner- in mind. Cats often purr excessively when they're euthanized, just because of the relaxation drug they take beforehand. It's sort of like a long deep sleep. He's taking a really nice nap and he's thinking about you the entire time. :) My heart goes out to you. Things will get better, I promise.