I haven't read this but reading the summary i-
He gets hard by eating
I was quite unsure about reading this myself as the description was quite poor and in my new found opinion sort of misleading. I personally believe the author was trying to say that his condition is this way now due to his own psychological problems and the connection of stress eating that he has convinced himself that he can't eat anything without triggering a hard on and less about any sort of real disease or physical condition (except maybe a self induced one due to his psychological problem). I hope this helps clear some confusion.
That little cunt... He wants his dick smash off!!