Woman have had a regular period their entire pregnancy before. It can be normal but not often does it happen. I would say just wait to see what your next blood work shows. If your doctor did not seem to be worried then I wouldn't stress too much right now.
Im 6wks today. I had bleeding last monday and it stopped pretty quickly. I panicked thinking i was having a miscarriage but since it stopped and i had no cramping im pretty sure it wasnt. When i googled bleeding in 1st trimester it says its actually very common and can be quite a few different things, one is subchorionic hematoma, or SCH pregnancy which is a blood clot between the uterus and placenta that bleeds out. It doesnt hurt the baby (Google it).