26 weeks tomorrow what's the normal weight the baby should be??

laken

so I went for my anatomy scan Monday and when the nurse practitioner came in to discuss it with me she explained that they wanted to send me to a high risk doctor for a more detailed ultrasound because they think that the baby is on the small side. well when I was in my ultrasound the lady said the baby weighed 1.9lbs and I thought that was great because the app said 1.3lbs. I have not been told an exact due date from the start iv always went by the first day of your last period and I'm getting confused and worried but at the same time I'm getting impatient for this second opinion because I want to know if baby is ok or if I need to be aware if anything or complications in the rest of the pregnancy. Any suggestions? I'm worrying myself to death over this. Anyone else been through this before that may be able ti help?