It is posdible to have negative pregnancy
test in spite of being pregnant and there could be various reasons for that.
Pregnancy test depends upon the presence of HCG
hormone in urine and sometimes not enough HCG hormone is thete in urine.
Other reasons could be expired test strip
However there are various other means by which you can confirm the pregnancy.
You can get a blood HCG test done which is very reliable.
You can also get a transvaginal ultrasound
done which can show the pregnancy.
You must discuss about these with your doctor.