What Causes Cramping, Nausea, Breast Pain With Moodiness And Nipples Darkening?

i had unprotected sex aprox a month ago (when I was fertile), i started taking the pill after this (Cilest) i have since had my period which was how it usually is when I'm in the pill, however I had cramps, I've also had nausea, been moody, and had pain in my boobs, I noticed today that my nipples have become darker... last week i took a pregnancy test (just to be sure) and it was negative... what could be wrong with me?