For a long time, people didn't understand what having a period was all about. They invented stories about it because they didn't know the facts. A lot of those stories are still around, but they aren't true. Losing normal menstrual blood doesn't make you weak. Menstruation doesn't need to put you in a bad mood.
Women can enjoy sex while they have their periods.
It is possible to become pregnant before your first period. It is possible to become pregnant when you are bleeding. It could be spotting after ovulation instead of your period. You don't need to stay in bed on the first day of your period. Cold drinks, showers, or baths do not cause menstrual cramps.