He's, as definitely evidenced by the books, not just a Stalker With A Crush. That's not always a bad thing, actually. It could have been interesting, creepily enough.
But what he is is actually rather abusive. He drops Bella like a hot potato once and she, the "caregiver", loses all hope and care for the world, and completely melts into a catatonic state, basically.
He knows about the effect he has on her, yet he leaves her on her own. I know people quarrel, and there are a lot of factors.
One, because Bella is a weak character, and spontaneously collapses without him; two, because