I am 7 days late on my period, and negative pregnancy test?

I was supposed to start my period 7 days ago! I've always had them every 28 days like clockwork! I took a pregnancy test at 4 days past my expected period and it was a negative!! I do have unprotected with my bf and he did come in me sometime last month! The only symptoms i may have is missed period, mood swings( bad! Ill bith about stupid stuff and i notice it being later in the day...ive never even been like that towards my bf before!), and my started hurting..even if theyre not being touched, and i cant seem to concentrate on anything or keep things in order like normal! anyways if i was pregnant shouldnt it show positive already!