See how symmetrical your body balance is as follows:
1. stand with feet heel to toe in a line for 30 seconds.
 2 stand up tall, head above shoulders, don’t lean forward.
 3. Concentrate on the movement you …feel in your body – you will be swaying and subconsciously adjusting your balance.
4. Then swop feet so other foot in front for 30 seconds.
5. Can you feel a difference in how much you move or how difficult it is to maintain the position depending which foot is in front?
 If you are not sure then repeat the exercise with your eyes closed.
 If you feel a difference then your balance is not symmetrical and this will be affecting your horse when you ride. Horses can feel the subtle changes you have in having control over your body.
So how to help: You need to improve your core stability and balance in rider positions and movements. I will add some more info about how to do this to the website in the near future.
But to start –
1. practice sitting on a gym ball or really soft cushion and sit on your seat bones.
2. Feel you are sitting evenly on them by placing your hands under the bones.
3. Now move your pelvis back and forth slowly (i.e sticking your bottom out then tucking it under) then return to a mid position where your are on your seat bones and you are even.
4.Concentrate on keeping body up tall with head above your shoulders while you do the movements.