36 weeks measuring small

Today I went in for my 36 week check up... while my Ob did my ultrasound she mentioned that the baby was measuring about 2 weeks behind..roughly 34 weeks.. so she sent me to do a more detailed ultrasound to check the growth..now I’m going to have to get another ultrasound to follow up and start Nst (non stress test) twice a week. I can’t help but feel worried and stressed out that I didn’t eat enough for my baby because I have gestational diabetes and felt scared to over eat. She said he’s only about 4lbs ish right now. Has anyone else gone through this and what was your outcome if so? I just need all the prayers I can get.. just hoping for my son to come out healthy and ok..first time mom :(