Answer
If Earth gained mass, it would pull down harder on you, and you would "weigh more" as measured by a scale you stand on. Note that though you weigh more, your mass is the same, i.e., you haven't gotten bigger.
If the sun became more massive, your weight as measured when you stand on Earth would not change. You (and the Earth) are in free fall around the sun and its mass has essentially no effect on the force exerted between the Earth and you.
