Ok, Electric Blue,

First thing I would note is that your kick is limited by how high your knee is. If you lift your knee to belt hi, that is how high you kick. In order to kick higher you need to practice bringing your knee up. I would suggest doing knee lifts and tapping your shoulder with it. Don't worry about kicking right away. Once you feel the knee come up easily, just let the kick go. It will be higher.
I don't normally advise kicking high in actual fighting but practicing high has its uses. Basically, if you can kick high easily, your kicks anywhere lower will really benefit as well.
You might also try thrusting your hips forward just a bit. I refer to this a "lead with your belt." If you drive your hips in just a bit (not to be confused with an actual front thrust kick), the pad will move back a lot better.
Cheers,
Jeff G.