Trying for Baby #2

Hi ladies, so Friday I took a pregnancy test and it was clearly positive. I was not feeling well yesterday with a lot of nausea and unable to have a bowel movement I know tmi! But they did a ultrasound and could not see a sac which is normal because it is very early but what concerns me is that my blood can back with a hcg of only 8.9! The ER dr proceeded to tell me that he thinks I am miscarriage could this be true I'm trying to stay positive but freaking out at he same time I have a appointment with my fertility dr on Tuesday