What Causes Cramps,tender Breasts,back Pain And Tiredness?

I am on birth control and been taking it right but I started my period a week early. I started exactly a week ago and my birth control says I am supposed to start today. I usually start a couple days later and I am only on it for 3 to 4 days. Yesterday I started having cramps when I barely cramp on my periods, my boobs were hurting and having sharp pains, my back hurts and I am tired all the time. What does this mean?