25 weeks 6 days

Had my appointment today. Fundal height was 23cm, baby weighs 1lb 10oz..I’m low key stressing. I feel like I’m behind. I’ve had no appetite. My doctor said everything looks fine, but this baby is the weight he’d be at if he was 23 weeks. He’s almost 3 weeks behind in weight. Has anyone had this and the baby still be fine? This is my third baby so pregnancy is really wearing me down. I should add that I was underweight when I got pregnant so maybe that’s the case.