Can the burden of carrying a backpack make you shorter or cause problems with development and height?

The backpack you use can indeed cause problems with your height. Because of the strain it puts on the spine discs can become compressed causing not only pain but for the spine to become curved. An over the shoulder bag (or a normal bag worn improperly) can cause one shoulder to become stooped compared to the other giving a person an off balance appearance. Although, it would most likely be rather subtle to the eyes but cause many complications later on in life if untreated.