Besides pregnancy what can cause a late period?

Late periods: Other causes of late periods include stress, which disturbs your hormone cycling, excessive exercise (like a marathoner), anorexia nervosa, premature ovarian failure, scarred cervix, ectopic pregnancy, endometriosis.

Many possible causes: Not ovulating (releasing an egg) 'on time' makes your period late. Causes include polycystic ovarian syndrome (pcos), underactive thyroid, excess prolactin hormone, aging of the ovary (diminished ovarian reserve), or low hormone levels (hypogonadism) from heavy exercise, eating disorders, or stress. See an ob/gyn for testing, or a reproductive endocrinology / infertility md if trying to conceive.