Small baby has me stressed!

So went to the doctor on Oct 18th at 30 weeks and was told my baby measures at 28w3dayd…

At 30 weeks she’s measured 2lb 11oz I’m currently 5’1 and was 126 pounds last appt I was underweight before pregnancy. I go back the 10th for another measurement but I just feel sick to my stomach. I want my baby to be healthy and able to survive I’m so afraid and can’t shake the feeling. Has anyone had this issue and have a good outcome? Any recommendations..,