Responses
I think what he meant was that his father took him to the doctor because he was "ill" because he was gay, but never told exactly that to the doctor. So, the next time he saw seungho he saw him truly ill, not because he was gay but because he seemed unstable. Probably seungho got some kind of shit going on with his father because of him being gay and that's what actually made him sick.
Mmm could also be possible
I saw that alot of people are saying that he takes medicine because he's gay, and to "fix him" that could be possible, I also think he could have been abused or even raped since the person saying why he takes the pills say he was never the same after coming back from somewhere. That could explain why he gets aggressive when he doesn't feel in control over his emotions and situations... (⊙…⊙ )