The former "Bachelor in Paradise" star was shocked when Brooks' pediatrician expressed concern about the child's weight being too low.
"We went to Brooks’ four-month checkup and I was crushed to find out he’s in the 5th percentile, and that the (pediatrician) was very concerned about his weight gain," Roper wrote next to a photo of her holding her little boy.
"I’ve never felt more like a failure," she continued. "The feelings of guilt that my baby was aching for food and nutrition, and I didn’t know it, consumed me. I knew he was a string bean (he’s tall for his age), but with how hard we work on his feedings, I guess I didn’t think he was that tiny compared to other babies his age."
Roper and her husband, Tanner Tolbert, welcomed Brooks in a surprise home birth in July. The couple, who fell in love in 2015 on the second season of "Bachelor in Paradise," also share a daughter, Emmy, 2.
The pair's "feeding journey" with Brooks "has been a really hard one," said Roper.
"We’ve dealt with dairy and soy allergies that left him crying for hours on hours from malabsorption, a lip and tongue tie we were advised not to revise (although they give him a poor latch), milk supply issues, foremilk/hindmilk imbalance. It feels like the list goes on," she wrote.
The “Mommies Tell All” podcast co-host said caring for Brooks and Emmy at the same time has been challenging.
"It can be hard to fully give your attention to each child sometimes when you are taking care of a baby and a toddler too, and I feel so bad I may have been missing some cues from him I didn’t know he was showing," she wrote.
"I’ve changed my whole diet and so many other parts of my life to make sure he is getting good feedings, so it’s just so hard to know that it’s not enough," she added.
To put more weight on Brooks, she's now following her pediatrician's advice to supplement with a hypoallergenic formula after every nursing session and to add extra feedings to her son's schedule.
"Any mamas out there that had babies that were on the lower end of the weight percentiles?" she asked fans. "How did you get through the worry and the guilt? How did you not over obsess with the progress?
"There’s been so many tears over here, but we are strong and working on getting this little guy some rolls. I’d do about anything in the world to help keep Brooks healthy and thriving," she added.