Baby measuring big!

Vanu
Hi ladies, I just had my 28 week ultrasound done, my baby girl is measuring 3 weeks ahead and weighs 3 pounds 11 ounces! My doctor thinks I might have gestational diabetes and is sending me to get the 3 hour glucose test done. I am worried now being ftm :(. Has this happened to anyone else? Did you have gestational diabetes or the baby was just bigger? Please share your experiences. Also How do I prepare for the test? TIA.