Missed miscarriage

So I'm extremely confused my last period was November 9 I showed up positive for a pregnancy test on december 4th. My first sonogram was January 13 where I would be 9 weeks when we went in she couldn't hear the heartbeat we had another ultra sound done later that day and she found the baby and it was measuring at 6 weeks the only bleeding I've has was when I first found out and it was a dark brown and it only lasted a day. My hcg levels were 1680 and i have had cramping the whole 9 weeks but no bleeding has anyone else gone through this?

[Desireeb]

Also the doctor said I could've had a miscarriage then got pregnant again