Bsha’ah tovah!
There is a halachic dispute as to whether a pregnant woman is halachically considered a mesuleket damim (one who is presumed not to bleed) once she has a positive pregnancy test, or only after 90 days have passed since conception. The practical ramification of being considered a mesuleket damim is that she does not observe a veset kavua.
Since there is doubt whether you are required to observe the veset kavua, and since you did not experience an actual flow last month, only staining, there is room for leniency in observing this veset. If the veset day has already passed, you may treat it as a veset she’eino kavua and you are considered tehorah. You do not have to perform a bedikah retroactively. If the veset has not yet passed, you should perform a shallow bedikah during the veset. You may shower first and wait 15 minutes before performing the bedikah. If you do find a stain on the bedikah, do not assume it rendered you niddah, rather you should bring it to a halachic authority for evaluation, explaining your situation.
If you were not rendered niddah, you should continue to take precautions against becoming niddah from any further staining by wearing colored underwear and waiting a few seconds after urinating before wiping. See our article on stains for more details.
We also recommend abstaining from intercourse for 24 hours after finding a stain so your status may be fully clarified.
If the staining gets heavier or doesn’t let up we recommend consulting with your doctor.
Please feel free to get back to us with any further questions.