How would your weight change on the surface of an earth sized planet whose mass was greater than earth's?

The way you describe the new planet, the situation would put you
the same distance from a greater mass than Earth's. 

Weight is directly proportional to the product of the two masses, and
if the distance between them doesn't change, then the weight depends
ONLY on the product of the masses.

On the surface of that planet, your weight would be greater than what
it is on Earth.  (It wouldn't change while you stood there.  It would just
be more than what you weigh on Earth.  Your legs would get tired ...
if you could walk at all.)