Measuring a week off

Cierra

On April 1st I had heavy bleeding and felt like I was getting my period cramping back and all. A couple hours after I started feeling VERY sick I felt a rush of liquid and knew it was blood. I went straight to the er and they saw a sack but no baby, I was 5 weeks and early enough that they said I shouldn’t worry. The day after the bleeding my morning sickness 100% went away and I felt so normal again and had myself convinced I miscarried. Today was my first appointment due to the bleeding and baby has a heart beat of 105 and is measuring 6 weeks! So reassuring but now I’m worried about being a week behind what I thought. I was. My last period was February 19th which would mean 6 weeks, 4/5 days (according to apps and internet searches) but I’m 4/5 days off. Is this normal? Just worried ever since I bled. Anyone else measure lower than excepted? I also have bleeding (left sack) and a cyst on my ovaries. My hcg levels are also increasing but not doubling every 48 hours like you’re supposed to. Just worried ❤️