Help!

So, my last period started October 23. My period was due November 20 i have NEVER been late for a period i am always right on track. I took a home pregnancy test Sunday and the line was very faint. I called my ob Monday morning and went for a blood test but it was negative. I still have yet to get my period and it is now a week late i am having almost every pregnancy symptom but as the nurse at my doctors office said “you’re definitely not pregnant!” Has ANYONE gone through this? Is there something wrong with me???