after chemical pregnancy do i need to undergo d&c?

Hi,
Welcome to ehealthforum,
The urine pregnancy tests done very early in pregnancy can fail to show you positive results as the kits are calibrated ones, so unless the hormone levels in urine reach a certain level, they do not show positive results. The lighter and altered bleeding could suggest possibility of decidual bleeding. Consider getting repeat blood/serum HCG test done along with serial HCG estimation (if the beta HCG test comes as positive). Doubling up of the hormone levels in 48-72 hours will show that pregnancy is going on smoothly. If levels are not adequate, then external hormonal supplements would be considered to be started to help you in preventing miscarriage/threatened abortion. An ultrasound scan done will also help to confirm gestational age of fetus/baby along with fetal wellbeing and viability.
If pregnancy gets rule out, or if the HCG estimations do not show rising levels, or if ultrasound scan reveals products of conception within the uterine cavity, you might have to undergo D&C procedure to clean up the uterus and stop the bleeding. Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet and lifestyle.
Take care.