Lyric discussion by MaynardNReznor 

Cover art for Home lyrics by Nine Inch Nails

He's clearly addicted to cocaine again.

It's a direct reference to a song on his first CD, "Sanctified" in which he is talking about his cocaine addiction.

In Sanctified, he says, "If you say come inside I'll come inside."

In this song, when he says "And I am still inside you," he's still addicted to cocaine.

The song is about all the times he has tried to break the habit, and he thought he should have by now.