Hi, - Any physical & psychological stress causes hormonal disturbance to lead to irregular periods. - Antibiotics too hamper available estrogen for continuing regular menstrual cycle... by slowing down estrogen metabolism / estrogen activation by good bacteria( being damaged by antibiotics)is also hampered by antibiotics, Thus less estrogen is available for building up of uterine wall, ovulation is delayed or dropped & menstruation is delayed or dropped. You had a prolonged course of antibiotic..so you are likely to have menstrual delay.... which would get back to normal after the reverting back of metabolism to normal. Taking probiotics ( Lactbascillus preparation facilitates this . ) Thanks. Thanks.