6weeks after IVF/FET scan show baby 5wk+

Second scan after 6week passed FET. Last scan 2weeks ago seen yolk sac only. Today scan show baby with heart beat. But still say it’s about 5week+ and slow heart beat. I was still put in risky stage and asked to come back two weeks later. Dr say there’s nothing much I can do. Just wait for next scan to see improvement. This is my first pregnancy. So anxious. Is any mummy experience before? Any tips for healthy baby growth? My calorie intake is about 1400/1500 cal. Now I am thinking to eat more. #firsttimemom #advicepls #firstbaby