What Causes Delay In Menstruation And Sensitive Nipples?

I have not taken a pregnency test but everyone keeps saying im pregnant im not all that sexually active my partner is older but we did have sex like a week before i was supose to get my period and no birth controll or condom and he cam einside me :S NOW i usally get my rag on the 20th to the 22nd and i totaly skopeed january and we are on to the 4th of febuarry i get so like cramps almost as if i was getting my period but i havnt and i have had really bad diharriea for like 5 days now my boobs feeel really heavy and supper sore but they alternate like somedays ther not sore but some days they are Also my nipples are supper sensitive wih isnt normal! ?? do u think im pregnat or is my period just hidding