Measuring one week behind

Dasha

Hi guys. So I am pregnant for the 4th time. First 2 were miscarriages and then I had a heathy girl a year ago. I was measuring with all 3 of my previous pregnancies behind, but this pregnancy seems that I am a week behind. I went for my first scan today thinking I am 7weeks 5 days but I am measuring 6weeks 5 days with the heart beat of 118. So that means I found out that I am pregnant at 3weeks and 3days(very faint line). Is that even possible? Should I worry about it? I am so anxious about it, I just want my baby to be ok🥲