Is it bad to wear my corset/waist trainer all the time except for showers?

Yes: This leads to core muscle weakness and predisposes you to back injury. Start core exercises as soon as possible and kick the corset.

Do you have any idea: What you are doing to your body ? Tight lacing (also called waist training or corset training) can cause shortness of breath, fainting, indigestion. This practice can decrease lung volume (requiring intercostal breathing). Relatively less use of lower lungs can lead to coughing. The liver is forced upward ; accessory lobes of the liver may form. Stomach volume is reduced ; the intestines are.