Weigh gain

I am 22w 3d and haven’t gained much weight. I am 5’6” and started at 115.4lbs and I am currently 120.6. I never had morning sickness so it’s not like I lost weight and am gaining it back. I eat a pretty decent amount of food every day and RARELY skip meals because I am hungry and I also snack frequently. We don’t have much junk food in our house, just some chips so I am eating pretty healthy. It’s starting to concern me that I’ve only gained 5 lbs and most of it was from week 10-16. I have been 120 since about week 18/19.

Is this normal? My baby has measured a few days behind since 8 weeks. At one point he measured over a weeks behind. My OB was excited at my 16 wk appt when she though I weighed 122 but really I was 117 and her scale just needed to be recalibrated.

Any suggestions? My OB isn’t super concerned but she was a bit disappointed when she saw I really haven’t gained much weight.