About to have my period or am I just late or pregnant?

Last month I started the first week of may. may 5-7th and it's now June 6th and I haven't started. For three, maybe four days now I have been cramping a little. Yesterday my lower back starting hurting and especially today when I woke up. And yesterday and the day before I didn't have a BM when I always do in the morning. No sore breasts or feeling nauseous.. But when I say, "Oh SO I'm going to start my period." I always start the next day.... Not this time. Do you think I am just late or could I possibly be pregnant..?