Can stress and excessive worry cause my menstrual cycle to last longer and have cramping for more days this month?

Yes they can.: Irregular periods and spotting 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).