Im so tired of this...

I'm 3 weeks late for af. I've took 4 pregnancy test and still no positive. I know periods can run a bit late. But mine have never been this late. Yesterday my I was cramping so bad in my ribs it hurt to eat. It wasn't period cramps either. Those last forever before I start.. these pains were really short pains.. I'm not getting sick but my boobs Reallllyyy hurt. Could it just be af?