Intro & Question

Hi I am new to this board, my LO is three weeks old today and a week ago we switched to strictly FF after much contemplation. Anyways, she has been back up and past her birth weight since two weeks old and has always been on scheduled feedings (every 3 hours). I would like to try on demand feeding with her, but I just don't know where to start. Do I continue to wake her every 3 hours during the day and let her wake on her own at night? I also have a hard time keeping her awake after some of her feedings during the day. I don't know if I should be trying more to keep her awake after bottles or just let her sleep if she is tired. I'm a FTM here so any advice would be great!