what’s the incurable disease that he has?

This is just my theory, but I think it's not really a disease. It might be because he was separated for a long time with his "fated" partner or "mate" that's why he's getting those symptoms

Well it has something to do with that too. In the novel it explained that he had totally lose control over his pheromones that's why he's taking bug dosage of inhibitors. So basically he is like drowning to his own pheromones.

Ohhh what is the title of the novel?