What causes one to have less days on going to period than her normal days, then to have little blood than an usual flow

A menstrual period that is shorter in duration and lighter in flow than usual can be caused by several factors. Hormonal fluctuations are common culprits, often influenced by stress, significant changes in diet or weight, intense exercise, or the use of hormonal birth control. Early pregnancy can also manifest as light bleeding, known as implantation bleeding, which is typically lighter and shorter than a regular period. High levels of stress can disrupt the body's hormonal balance, affecting the menstrual cycle. Additionally, conditions like perimenopause, where the body transitions towards menopause, or certain medical conditions such as thyroid disorders or Polycystic Ovary Syndrome (PCOS), can lead to such changes. If these changes are persistent or cause concern, it is best to consult a healthcare professional.