What is happening

I'm 6 days late, I'm never late. My period is normally spot on, or the day before. But now I'm 6 days late, I took a test this morning and it was negative. My boyfriend is convinced I'm pregnant, because I'm really emotional lately. I've also been nauseous and having cravings, I've been really wanting things that I've never really liked before. what is going on with me if I'm not pregnant