Baby measuring small

Went today for a growth ultrasound found out my son is weighing under a pound that he is measuring behind it might be a problem with the placenta that I have to go back in three weeks for another to see if he gained at least 2-2.5 pounds if he gained that they will have me come in once a week for a growth check on him if not they will talk about inducing I’m trying not to worry I know I been having hard time eating 🍽 due to the heartburn but idk what else I can do to get him to start gaining