Yeah....the period thing really depends...and not only from woman to woman, but from baby to baby.
My first nursed every two hours, night and day, and it was a year before I got my first period.
#2...good sleeper at night..6 straight hours of sleep sometimes!! My period was back at 3 months!!! I was so disappointed, but I'll take sleep over having a period any day.
#3...almost at 3 months and no period yet. I'm crossing my fingers it'll be awhile yet!!! However, he does go awhile at night (I've turned the clock down so I have no idea how long.
Regarding the tiredness, no telling! Take it easy and if it gets any worse you may want to get checked out.