The stability of your mid section of your body is so important in the swing, as it links the movement of the upper body and lower body.
All good players should test themselves in the area of pelvic and core stability. To do this exercise:
Lying on your back, bend both knees. Raise your pelvis from the floor and hold your body in a straight line. Then slowly straighten one leg.
If you can’t then Do this sequence of lift and hold 10 reps 10 sec hold try and do it three times per week to see an improvement.