I'm 6 weeks pregnant, since yesterday evening, I have some spotting n light bleeding with cramps

When to KKH, during the scan doctor claim there is nothing visible in my womb, she did mention 6 weeeks is still considered very early stage. Did urine n blood test, I'm still positive of pregnancy. The HCG level is also low. Need to go back on the 19th to give blood again. If there is a decrease in the HCG level, high possibility of miscarriage or ectopic pregnancy. I'm extremely very worried. Any mummy experience this b4 and did u carry the pregnancy for the full term?