34 weeks and measuring small (advice?)

I haven’t really posted much about my pregnancy because it’s been going fine other than some really bad vomiting, but the past few weeks have been hectic.

At 30 weeks I was diagnosed with gestational diabetes, and was put on a diet plan and told to watch my sugars, I’m to prick my fingers 5 times a day (which i struggled with and still kinda do, but for the sake of my baby boys health, I do it). Yesterday I went for my ultrasound due to GD so they could check my boys size, the tech was super sweet but was concerned because my baby is measuring pretty small, even with GD, he’s about 3lbs and 4oz (for reference I’m 34 weeks), because of this they want to do ultrasounds twice weekly so they can perform a BPP test on him. This stresses me out because I really want my baby to gain the weight he needs, but at the same time I’m to watch how much sugar I’m intaking. I have no idea what foods to even eat anymore, or what I can do to help him gain weight. My ultrasound tech asked if I was a small baby and I was (I was 4lbs 6oz and my SO was around 5lbs). I could just have a small baby. I feel like I’ve done something wrong and maybe that’s why he’s behind in weight? I was told he was perfectly healthy other than his size. I’m at FTM and I just need advice and to get this off my chest, is there anything I could do to help him gain weight while also watching my sugar 😩

On another note, we got to see his sweet face and learned he has hair, I’m so in love with this little boy already, I can’t wait until he’s here.