Belly isn't getting bigger

Im 32 weeks and I dont feel like my belly has gotten much bigger over the last several weeks. I have really been watching what I'm eating this time around so my weight gain is around 21-22lbs and i'm definitely eating enough. At my 30 week appt by fundal measurment was 29.5cm which isnt anything to worry about but that was the first time i was measuring "behind" my midwife wasnt concerned at all. But all i have heard this pregnancy from everyone is how tiny i qm am they can't believe how far along I am. I'm starting to get a little worried because i take weekly pictures and i really dont see much of a difference at al week by week. I just laid down and measured my stomach and it was only 27cm.... I know how to measure it and Idon't  think I did it wrong, it's pretty simple. I have abother appt in a few days and I'm going to mention my concern but i really feel like i need to have an ultrasound. I havent had one since my anatomy scan at 20 weeks. I know he is okay in there and moving around like crazy but i really feel like i need some reassurance. In this picture i was 24 weeks on the left and 31 weeks on the right.