Failure to thrive

Are there any moms willing to share their experience with failure to thrive? I feel like my baby is doing great. He’s meeting all of the milestones he should be, and he is gaining weight. Just not at the rate they want. He only gained 1 lb 12 oz between his 2month and 4 month appointments. So, we’ve been referred to a GI specialist. The appointment is next week. I’m just not sure what to expect from here, and I was interested in hearing about other’s experiences.

Here’s a blurry picture, since he never stops moving these days 😂🥰