Please help?!

I am supposed to start my period in a week from tomorrow - my periods are extremely consistent from using the pill. Today I slept until 2:00 pm and I never sleep past 9. My breasts are insanely tender and I've been really constipated. I've been spotting pretty heavy today as well which is atypical for me. It started out red with clots then got darker and that only lasted a few hours. Does anyone have any idea what is going on with me? Also note that I missed a day of birth control so I am wondering how that could affect things. I am sexually active too so I don't know if these are early pregnancy signs or early period signs or what. Please help.