Neg beta hcg- what else could it be?

Ashley
So I'm 11-12 days late from af. Went to the dr, told her my symptoms. She drew beta hcg, CBC, and thyroid levels. Negative hcg, and everything else is fine. Now comes the part where we try to figure out what's causing my symptoms (right sided abdominal pain that radiates to my shoulder, nausea, dizziness, feeling like I have the flu/fever)... Anyone else every had this?