There are chances that you may still be pregnant and the hormone HCG
is low to show up.
Please wait for another week and redo the urine pregnancy
test. To confirm it, you can always get a blood serum HCG levels done which can precisely say about pregnancy.
If the HCG tests are negative, then there may be hormonal
imbalance causing the delay in periods. In such a case, consult your gynaecologist and you may be prescribed oral contraceptive pills
to regularize the cycle.
Wish you speedy recovery.