Should I be worried!!?

Savanna

I found out I was pregnant three days ago and I logged it in and it calculated that I’m 6weeks n 3days but I went to the er yesterday due to some cramping in my lower abdomen and they confirmed my pregnancy and they gave me a hcg blood test and the dr told me my result for my hcg test was 147 , n he said that’s low for 6weeks so ..does that mean I’m like 3-4 weeks pregnant or am I gunna have a miscarriage!? I’m so worried