Dont know if this is a period

I started what I thought was my period 5 days ago. Its was normal the first day and a little into the second. The first day I passed some hunks of tissue and since then the bleeding has gone to very little. I normally fill several tampons a day for the first 4 to 5 days. I thought I was pregnant but the bleeding started now I still having symptoms??? veiny breast, pinching cramps, back ache, dizziness, some nausea but not as bad as it was and no appetite. Symptoms usually go away by the second day of my period. I'm getting negative test. Has anyone had this happen before?