Early period

I got my period today and I wasn't supposed to until wed which is 3 days from now. It's not that heavy it's just light. I can wear a liner and be fine. My last period was the same but only a day early. So idk if it's normal to be 3 days early. I have been having cramps for about a week now. And today I have frequent cramps that are somewhat bearable and my right boob is sore but only Bc my bf accidentally elbowed it bad.