Speaking as someone who personally hasn't seen you ride, filming yourself is a great place to start. Make sure your not throwing yourself forward and trying to jump the jump for your horse (this actually makes it harder for them), but your position is only as forward as it needs to be, and your weight is in your heels.
What @karinalipnicka said, but you also want to bring your body forward, and not down (I don’t know if that makes sense) so instead of throwing your shoulders at your horse, rather ‘lean’ into it. And keep your chin up!
Riding without stirrups to get your hips open and seat more secure and before jumping have few laps in all paces standing up in your stirrups to get your leg on and make it more secure
Also when jumping think about folding your body instead of standing up in stirrups. Usually you want your stirrups length to get a 90 degrees angle of your leg however that is way too short for me so I go a hole shorter (its up to you). Obviously stirrups should be a bit shorter than for flatwork to help u fold and pick yourself up.