sub chorionic bleeding? has anyone heard of this?

Terra • Married to my Mr. Right. Mom to my IVF heart warrior daughter born November 16, 2017.
So today I was sitting in bed got up felt something wet went to check and was pouring blood! I'm currently 6 weeks and 4 days. Called the clinic emergency line and was advised to go to the hospital. After sitting in emergency for what felt like forever bleeding like crazy we finally saw the Dr and got blood results. All my levels were fantastic hcg was 68,000! He checked my cervix it was still closed wasn't sure it was a miscarriage at this point. Sent me for an ultrasound where I got to see baby and the heart beat! It was 127! I couldn't believe there was still a little baby growing! Dr said it was from the placenta trying to implant? I don't fully understand but said it's not much to worry about as long as the bleeding is minimal. He said I will prob bleed on and off for 1-2 weeks still! Honestly this was the most scary and emotional day so far! Has anyone else ever had this?