Since you did your urine pregnancy
test only once,you should get a repeat pregnancy test done and preferably with morning urine sample.
A negative repeat test would rule out pregnancy.
Thete could be other reasons for delayed periods like stress
,obesity,recent illness,hypothyridism,change of medication,change of schedule,hormonal
It would be best to consult a Gynecologist for thorough check up and diagnosis.
Treatment would depend on the cause.