DKdc,
It all depends on your string wrist position!! IF you start the draw with the wrist OUT, the elbow will already be behind the arrow and IF you maintain that wrist position, the elbow will remain behind the arrow.
It sounds like you are doing it backwards ( VERY common). You don't move the elbow behind the arrow AFTER reaching anchor, you put it there BEFORE the start of the draw. In addition to the Video Tradcat mentioned look at "release tips."
Arne