On bc. not sexually active. period cramps and feels like im on period but period has not come at all. why?

Your hormones are in: .. flux for some reason, so hang on for the ride. Irregular periods and cramps could mean you may have some hormonal imbalance that could be affected by many different factors, including age (if approaching menopause?), nutrition, illness, exercise (or lack of it), body girth, psychological well-being, stress, season, or simple fluctuations of other related hormones (thyroid for example).