Not gaining weight

Courtney • I'm a stay at home mom and currently working towards my degree in nursing.
Had my 32 week appointment today and I've only gained 10 pounds this entire pregnancy. My uterus measurement is just right for 32 weeks. Her heart rate is good, too.
My doctor said she doesn't suspect anything, but scheduled me for a fetal growth ultrasound. 
I only gained 20 pounds during my first pregnancy and with a little over a month left until my due date, there's still plenty of time for weight to be gained.
Even with this in mind, I can't help but feel a little nervous/anxious. Guess I'm just hoping to hear from people who've been in the same sort of situation. The soonest radiology could get me in is February 26, so it's a bit of a wait. 😖