I'm nervous looks like 3 weeks ahead ๐Ÿ˜ž

I went in today for my 28 weeks and 4days checkup and my doc said my baby is like ย measuring 3weeks more than what it's supposed to I'm freaking out cause not to long ago they told me I have diabetes and now I have a ultrasound next week has this happened to any one oh I'm measuring 31 weeks ๐Ÿ˜ž can you tell me your guys experience if it's happen to you and what do your ob gyno does next ?