What Causes Delayed Period And Soreness In Breasts While HPT Is Negative?

Hi, so normally my period cycle is a month and a week after my last period. I was supposed to get it the 16th of this month. But I didn t. My boyfriend and i practice safe sex with a condom, but I m starting to worry now that it hasn t come and now my breasts are sore. I took a pregnancy test last week and it was negative.