When it is clear that bleeding is from a urinary tract infection (UTI), then it does not render a woman niddah. If it could be from the UTI, then the answer depends on where a woman is in her "halachic cycle" (e.g. during the shivah neki'im or after the mikveh).

Given that you are pregnant and that your doctor has identified your bleeding as non-uterine, you may indeed assume that you are not in niddah.