Thanks for the query.
The scanty flow during periods can occur due many causes.
Anemia, PCOD, thyroid abnormalities, prolactin
hormonal fluctuations are few of them.
So just by symptoms we cannot confirm or rule out the pregnancy.
You once go for blood test
for pregnancy which can give more accurate result compared with urine test.
If the test comes negative, consult gynecologist and go for ultrasound
once to find out the possible causes that are affecting the fertility
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429