Hcg levels

I went in to get checked because I was late on my period and got a positive test. Did a sono and they told me I was measuring under 5 weeks. Next day I got my blood work done to get a better understanding. They called me with results saying they were at 19000 and she was a little concerned because my sono was measuring so low with high numbers. I came in and got blood work done again. So they called me and told me it raised to 27000 but this was a 5 day time frame. Doc told me she’s not very optimistic with this pregnancy because my numbers aren’t as high as she was hoping. Getting more blood work done on Monday along with a sono. Has anyone gone through this?? I’m trying to be optimistic but it’s hard when she’s telling me to be prepared if I get bleeding. ☹️