Low hcg ???? Help

I had a miscarriage April 8th. Then my level was 24.0, only about 1-2 weeks along then. never went in for a blood test until May 8th and the blood test said positive and so did 4 test. Dont have Insurance so I went into Er, he did a blood test and said my level was 123, at first he misread them thinking it was much higher so they did a vaginal ultrasound and didn't see anything. Probably because way too early. He said he wouldn't think it was left over from my miscarriage due to it was 24.0 then and thinks I got pregnant again before my next period. I go back to get a blood test Thursday to see if it has went up. What do you all think??? Anyone else experience this???