Before the human race invented inside, most women's period were matched up with phases of the moon. During the new moon, they would have their period. The full moon is when they are the most fertile,...
No, being horny can't lead to any emotional or physical pain that would lead to any pains in the head, ex. headache. That would be totally a coincidence.
Because they are affraid you won't like them.
IN ADDITION:.
Boys mature slower than girls. The average boy matures at the age of 16-19. Sadly to say, girls mature at 14-18. So nature has been mean...