You're afraid of coming over the top and slicing or pulling the ball, so you hold your right shoulder back and swing from inside to outside.
Why that's a mistake
It's a risky play because at some point you must get your right shoulder through to the target. Otherwise, you'll get a swing that stops at the ball instead of going through it. Expect pushes and weak slices when you try to hold back.
The move you need
They key to producing straight, powerful is to turn your right shoulder through your left armpit line on your downswing. This enables you to explode through impact, release the club down your target line and finish in balance.
How to do it
Try one, or all, of the following to correctly get your right side through to the target without coming over the top.
1. At the top, think of replacing your left shoulder with your right. That will help you turn through while keeping your right shoulder under your head instead of spinning out in front of you.
2. Hold your finish. Check that the outside of your right shoulder points at the target and not in front of you (which is evidence of an unfinished swing).
3. Practice this drill: Place the head of your driver in front of your left foot so that your left arm is fully extended (parallel to the ground) and the shaft is straight up and down. Swing your right arm to the top of your backswing.
Swing your right arm down and, as you do, turn your right shoulder inside the shaft while keeping it under your left arm. This "under and through" shoulder turn is the correct way to hit past the ball and make a full swing with a powerful release.