Help! 5 month old still the same weight as last month!

Baby girl will be 5 months on the 11th. Last month she weighed 13.2 pounds. Our pediatrician didn't seem too concerned at her last visit 3 weeks ago that she was on the lower side of the chart for her weight. She explained some EBF babies tend to gain weight slower so I tried to tell myself not to worry too much. But now I weighed her and shes still the same! That was 3 weeks ago and she gained nothing. I feed her on demand mostly, we have started solids but very little and she doesn't sleep through the night quite yet so she never goes more than 3 hours during the day and 3 1/2 to 4 hours in the night without eating. I have had some worries it might be my supply, but I always seem to have milk when I self express, she seems to be swallowing normally, has a perfect latch, and has 6-7 fully wet cloth diapers a day. & she seems to be happy most days & is hitting & exceeding all of her milestones. So what's the problem here!? I have tried to up my calorie intake & started drinking those body armor drinks so hopefully within a few days she starts gaining again 🤞🏽 or I will call the pediatrician. Has anyone else experienced this with their LO?