Tiny belly at 30 weeks pregnant

Tara • Wife and mother to two boys💙
This is my second pregnancy and my belly is definitely smaller this time. I feel like it really doesnt grow much week by week but when i have my appts i'm always measuring right where i should be. This is so weird to me. I also haven't gained any weight in about 3-4 weeks definitely starting to get a little concerned. Has anyone else experienced this?