I dont know if im pregnant. Help!

Hi ladies!

My period was suppost to come 6 days ago according to this app and it still hasnt. My period is regular and doesnt change. i am feeling all the symptoms as if it is though: fatigue, very sore breast (specially nipples), and sometimes a light cramp on my lower abdomen. I do not have children so i dont really know if i could possibly be pregnant or not. Can someone tell me if these are signs of me being pregnant or is this just my period acting up?