I wear 3 corsets at a time (waist training) for about 20 hours a day and have been for a few months now. could this affect my menstrual cycle?

Corsets create that: hour glass look by squishing your internal organs and displacing them inward and upwards. They hurt your abdominal and chest organs primarily. The hip & pelvic bones tend to protect the pelvic organs. If the corsets are preventing you from eating or if you're seriously stressed out trying to achieve a look that isn't natural for you, they could affect your cycles indirectly. Not recommended!