What Causes Vaginal Bleeding During Pregnancy?

I m 16 weeks pregnant and have been bleeding for nearly 3 weeks straight. First started as gushes, then was period-like after first day, tapering toward end of the week only to get heavier again, recently slowing in last few days, but I have to always have pantiliner, as it has never stopped (tomorrow will be day 20). Pelvic exam indicated no infections, bleeding appeared to be from cervix. Two ultrasounds since bleeding indicate healthy active baby, no red flags to ultrasound tech. I just want to know if I should be reaching out to my dr. To let her know the bleeding still occurs or if there s really nothing more to be fine about it. Also wondering if I should be concerned for possible miscarriage, birth defect, or complications later in pregnancy/delivery. I don t go back to dr. For 2 wks but I m losing my mind not having answers or not knowing if there needs to be an answer right now.