Lots of no stirrup work to make your leg stronger! Also check your stirrup length ( usually that's the culprit) and maybe check the balance in your saddle (stirrups should be inline with the girth for maximum stability).
Work on no stirrup work! You can also temporarily (for about a month) tie your stirrups to the girth to retrain your leg placement. This with consistent no stirrup work should help! And don't forget that while you do no stirrup work, you should be focusing on engaging the inside of your calf!😊👍🏼