Because Edward has mind-reading powers and he cant read Bella so he sneaks into her room and watches her sleep to see if at night she lets her guard down so he could read her and since he couldn't read her the first time he comes back again and again to see if he could read her then.
because he loves her
Because Edward likes to watch Bella sleep
Edward sleeps with Bella, because he loves her.
Watching Bella sleep...
He watches Bella sleep sometimes
Romeo and Juliet
The first night that she knows Edward is there in her room with her.
Bella: No bed? Edward: I don't sleep. Bella: Ever
I'm not sure exactly what you mean but... he did get in her house and watch her sleep for a while so he probably might have looked around a bit.
In the Twilight series, Edward and Bella officially consummate their relationship in the fourth book, "Breaking Dawn," after they get married.
romeo and Juliet
He writs a Lullaby for Bella. Called, Bella's Lullaby. He plays it all the time and to help her sleep he hums it .