Your symptoms suggest that you may be having some medical disorder or some deficiencies.
I advise you to get yourself thoroughly checked up by getting CBC,serum B12,VIT D,serum calcium,thyroid function tests
,urine routine examination and x-ray LS spine done.
Get your pregnancy
test done again.
A negative pregnancy test may be due to some medical disorder and the reports will tell the cause.
Consult your doctor for the investigations and treatment.