My wife don't have period for almost 2 months, but she is not pregnant, she's working and stressful, please tell us what is the best medicine?

It depends on cause. If no period w/i 3 months she should see gynecologist. Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; over-exercising (endurance athletics), travel, significant illnesses, oral contraceptives ; other meds, illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., pcos).