At what week during pregnancy do you start looking heavier and gaining weight?

Depends on your wt. Weight gain in pregnancy and showing does vary based on your prepregnancy height and weight. Larger women may not "show" until later. Thinner women may start to have a mild baby bump around 16-20 weeks.
Depends. Weight and height are very important. Other factors are how tone you are and if this is your first pregnancy. First pregnancies show later, and following pregnancies show earlier. For women who are in shape and have toned tummy muscles, pregnancy may not be as obvious until later.