I've Hardly Gained A Thing! Should I worry?

Lexi • 26, married, mama of a toddler boy, not TTC ✌️❤️
Hi ladies,
I am 23 weeks and 4 days pregant and I am only 1lb above my start weight. I am average weight and tall - 5'9.
In the beginning I weighed 156.
I lost 5 pounds from bad morning sickness. Eventually I gained the weight back and now I am 157.
I am eating frequently and getting a lot of protein. Why am I not putting on weight?
Baby boy is measuring on track. Should I be worried? Anyone else have this no weight gain experience? What should I do??