Period boobs or pregnancy boobs ?

Okay so I'm 3 days late for my period & on the day I was supposed to start my boobs started to hurt EXTREMELY , like just to lay on them hurts however I have been getting cramps like if I had already started my period (I usually only cramp the night before and during) is there any way to indicate the different between your boobs hurting before your period & if you were pregnant? Btw my boobs never usually hurt &I; if they do it's usually not this bad ?