From what you describe it sounds like you aren't "grounding" (pardon me because I've only done European Greco Roman and my English wrestling phrases sucks) the force properly as in making the shot go from your muscle groups shooting away from the feet.
Seen it many times with BJJ artist that never really got the penetrating drive down properly since they forget to disperse much of the power and end up being the receiver of both the impact and force from the shot. Along with a stance that is too high you can end up not receiving much of the impact at all in anything besides your lower body.
Or, you can have a pre-existing injury or problem in your knees, my first thought was however that you're not driving through properly and end up receiving the shock in your legs and knees instead of your upper body (think slam).
That's what I've been working on improving for many in my club, it doesn't really matter which rank though I guess the ones above black tends to know so much about shock anatomy and how the body works to figure it out themselves.
Tell me what you think, I'd love to hear about any previous injuries you might have suffered as that will help explain the situation further. Any previous wrestling experience, changed your technique lately, recently started taking powerful shots and so on.
Let up on taking powerful shots and try to rotate the force along your base as with the lateral drop and such since it's technique bringing them down and not strength.
Watch yourself so you don't rotate with force in the drop with static feet though, had a guy do that and crack open his Tibia (vertical full-length break), looked like it hurt and it made me feel like shit because I instructed the guy about shots but forgot to mention that he should let his feet get off the ground if you put force in it.
There's far more technique in making good shots beyond just timing and force.
