Early testing in pregnancy can give false negative readings, so it may be worth waiting a couple of days and doing another test. Or ask your doctor to run a blood sample as this is more accurate.
Assuming pregnancy has definitely been ruled out; there are a number of other reasons for late or missed period.
These include hormone imbalance, Polycystic Ovary Syndrome, thyroid problems, stress, being underweight, or being excessively overweight, losing weight very quickly or exercising excessively.
In order to get an answer re hormone and thyroid you will need to request blood tests for these from your family doctor. The lifestyle factors can be looked at and changes made at home/work to reduce stress etc.
Your doctor will also want to hear about any other symptoms such as unwanted hair, mood swings, thinning hair, tiredness etc.
The spotting could be a sign that you are pregnant, and that a normal period will not occur, However it could be due to hormone imbalance so at this point we cannot be certain either way.