sounds like your having a problem with your pivot or post foot. when you rock back and turn your pivot or back foot, sandy koufax advocates wedging the ball of your foot against the rubber so you are pushing with the ball of the foot, not the side of your foot. hook the cleat under the ball of your foot in the front edge of the rubber. the sole of your post foot will be at about a 45’ angle against the rubber. most guys place the sole of their foot flat in front of the rubber and press or push against the rubber with the side of their post foot. if you were pushing a 50 lb rock with your foot, you wouldn’t push it with the side of your foot, you would push with the ball of your foot. you get a better mechanical advantage lining the bones of the ankle up with the bones of the shin. this tranfers the force directly into the hips which is what you want to do.
when koufax worked with hershiser, he had him take the ball of his post foot cleat out of his shoe to get the feel of where the weight should go in the foot. it took hershiser about 6 weeks to learn this. it’s all in the sandy koufax: lefty’s legacy book. koufax felt this was the most important thing a pitcher needed to get right.
after you get the feel for your post foot, make sure you aren’t arching your back and leaning toward 1st base with your upper body . you can check this by opening a door 1/2 way and going through your wind up with your post foot directly infrom of the door. when you get your stride leg kee to the top of your pump, what many call balance point, your foot hips and eyes should all be lines up with the edge of the door when it is in front of you toward the plate.
now, the first move from this position toward the plate (and there are different beliefs here) is to get the hips as far in front of the back foot and shoulders as possible while maintaining balance. you post foot, hips and shoulders will form a < if you are right handed. the bottom of the < represents your foot, the middle represents your hips, and the top represents your shoulders. this puts you in a very powerful position with good mechanical leverage in the big muscles of your body.
try this if it makes sense, get the book, it talks about it in detail. i think a video clip would be very helpful. if this helps you we can continue.