Venting

I had my 31week appt today and my fundal height is 27-28. So they did a sono to see how he is growing. He is only weighing 1lb 15oz and small for his weeks. I am just so nervous. Everything is healthy. Heart is good and brain and all looks good. He just isn't big like he should be. I feel like I'm doing something wrong. Or he isn't getting the food I'm eating! Agh I just don't know what to do. Thanks for listening. Rant over. Comment if you want. 😔