Head measuring small at 31 weeks

I’m now 32 weeks, we went for an elective 3/4D ultrasound and the tech told me her head was measuring small, but before said it was measuring big?!? She said be sure to tell your doctor. Granted I have gestational diabetes and when I told the doctor he said that was uncommon... so I’m going back this Friday to my OB to have yet another ultrasound to check her head circumference. All other US have been normal up until this elective one. However, my FH is right on point for where I should be.

I’m worried sick, this is my first baby girl. Any thoughts or opinions please!!!!!! Thank you!