Anyone with a confirmed pregnancy after a negative blood test?

Hi ladies! 
Has anyone here experienced a negative blood test but actually been pregnant?  
Currently I've had sore boobs for 12 days now and they are beginning to feel fuller.  I've also experienced cramping gassiness constipation. Hungry often and now backaches.  I testes a few days ago and both were negative but I've had no spotting recently to indicate my period is coming.