To be perfectly fair, having a period is a extremely fucking brutal process where girls shit blood and tissue from the vagina while having to deal with extremely unusual cravings they're aware is terrible and in pain roughly the equivalent of getting kicked in the balls when the time comes.

Every month.

And it could lead to permanent damages.
RL balls are not like cartoon balls that turn back functional after being hitted by an anvil.
Girls! If your boyfriend said you his balls are made of steel, he's probably talking metaphorically. Don't test it!