baby measuring small

Quanisha • Living life the way God wants me to and being happy
So I had a ultrasound done today and my baby boy measure at 2lbs 11oz and my doctor said he was a little small for me to be at 30 weeks and 5 days I don't know what going on but I'm starting to feel down about it I don't know if it's my fault or what I don't know what to do to change this outcome I just hope he will be fine by time he is born