Confused & Scared

So, I am 21-22 days late on my period. I have taken a few hpts; all negative. I went to the doctor a week ago for a blood test. It was also negative. I still am missing my period and I never thought I would miss it so much. I seem to be going through my cycle, just no blood. I have a pain on my left side that won't go away which is sometimes dull and sometimes very sharp. I am having backaches, headaches, fatigue and nausea... Idk what to think or what to do... Has anyone else gone through this?