Hi, throughout the month i am happy and healthy, but for one week now and again i am severely tired. i have fallen asleep twice in my car today, i have headaches that wont go away and constantly thirsty. im like a walking zombie, its interrupting with everyday life. but i never know when this period of symptons will set in each month. The only thing i take is 20mg of citalopram each day. but these symptons have been around for years.