cuz u fat.
The right side and the left side of the body are not the same size. Usually you have one that is bigger and you notice it buying shoes for instance when one shoe is slightly bigger then the other. A breast can also hang lower then the other so it seem larger.
the left side has to pump blood to the rest of the body
It is considered to be on the dorsal side of the human body.
one side of your entire body is small than the other. The left side is bigger right?
Because the pressure on the left side of human heart is higher than the right side of human heart.
the left side has to pump blood to the rest of the body
Its not. The heart is located in the center of the thorax directly behind the sternum. the reason it is often though to be on the left hand side is that the left ventricle is considerably bigger than the right and so sits a little further to the left than the right does to the right.
Humans, like all mammals and other vertebrates, have bilateral symmetry. This means they have symmetry across one plane (known as the sagittal plane, and directly down the centre of their body), which means one side of their body approximately mirrors the other side.
PCH=Lungs
the right side is bigger because it has to pump blood to the whole body
I dont know for sure but perhaps it may have something to do with your dominant side? you may use your right leg and arm more than your left there for it could make that side bigger/stronger but i do not knpw for sure so dont quotr me.