Bleeding at 6 weeks

I am 6 weeks, 3 days pregnant and have been bleeding since Thursday evening. It ranges from light pink to red, and is what I’d consider spotting or light bleeding, noticing it only when I wipe and occurring 1-3 times each day. I had an ultrasound and exam on Monday and everything looked good, including the baby’s heartbeat. They didn’t find any source of bleeding, and basically just told me not to worry about it unless it gets worse. I asked if it could possibly be low progesterone and they said because I already take 100mg of progesterone, I don’t need to take any more. I had a miscarriage earlier this year with similar bleeding and I can’t help but feel anxious. Has anyone else had bleeding with no known cause and it turned out fine?