Although you feel you are swinging well, your club is grounding or bottoming out before making contact with the ball.
The big muscles of your lower body MUST initiate the forward swing!
This will improve your weight transfer and help to increase club-head speed, and therefore distance. A more efficient weight transfer will also encourage a slightly later un-hinging of the wrists, thereby improving the quality of your ball-striking.
Corrective Drills:
Both of these drills are ideal for practice at the World of Golf target tees and will promote the feeling that the lower body is starting the forward-swing, not the hands & arms