Measuring small

I'm a FTM so may be more worried than I should be.... I'm currently 24w4d and just left my dr appt and dr said baby is measuring at 22 weeks. She said she's not overly concerned because I'm tall, 5'9, and have a longer torso so there's more room for baby. I'm still really worried tho baby is measuring 2.5weeks small. Anyone else have this? Is this normal? Should I not be as worried as I am? Thanks for sharing your comments/experiences!