My first period

It was a hot summer day and I was working in the yard for about Half the day. Eventually I went upstairs to take a shower , all of the sudden I start crying my eyes out for no reason what so ever!! Then my mom comes in with a concerned, caring look on her face. She asks me what is wrong? " I don't know I said!!" With my face covered with tears. The next day I started my period and everything made sense...