During my period and sometime before i experience pain in my back and goes down my left leg. what could this be?

Painful periods: There are multiple options. Hormonal treatments such as birth control pills, Progesterone treatments and the Mirena (levonorgestrel) iud are effective reversible treatments that will help many people. There is also a drug called Lysteda that contains no hormones which will help others. We can always determine why each individual hurts in different ways during their period.