If the radius of earth decreased it's radius, with no change in mass, nothing would happen to your weight, though you would be much lighter, due to lack of gravity.
the reason the gravity on the moon is so much less then the gravity on earth, is because the moon is so much smaller then earth.
The smaller the planet, the less the gravity, the bigger the planet, the heavier you are, due to gravity, not due to your personal weight.
