I usually get my periods after every 21 days strictly but from last 3 months I've completely missed them I had taken emergency pill last in February in March I got my periods properly but started facing issue in April I consulted a gynac by the medication I got periods for that month But again this month I've missed it I'm not sexually active nor I've taking any emergency/birth control pills from February but I've some burning sensation while urine I've frequent urine problem and even my thyriod is normal Then what is the reason for missed periods??