Thanks for the query.
There is possibility of miscarriage
as sometimes as sometimes urine pregnancy
test kits may not detect the early pregnancy.
So you better consult gynecologist once, get examined and go for ultrasound
to find out the possible cause for your problem.
If there is any signs of incomplete abortion
you can proceed further according to your doctor's advice.
If there are no signs of pregnancy and features of infection noted you need antibiotic course.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429