Period 2 days late, bfn...

traveled for a wedding this past weekend. The day of the rehearsal, the day before expected period I woke up really nauseous and stayed nauseous for hours. The day of the wedding I didn't start bleeding, I had cold chills, cramping, really bad headache and I almost started crying when someone was talking to me. I felt really hormonal. Today my period is 2 days late and pregnancy tests are saying negative. Anyone else have this happen and still been pregnant?