Help! Eating problem

We started solids when she was 5.5 months because her ped was concern of her weight. She went from 20th percentile to 4th in 5 months. At first, everything was going so smooth. She loved eating. We tried bananas, broccoli, sweet potato, and blueberry oatmea. Then i tried avocados and she hated it. And then she had trouble pooping and was constipated for 6 days. Gave her prune juice and still she didn’t go. Ped told us to give her pedia lax, since we were so desperate, we gave her it. After that, she refuses to eat anything i give hwr until now. I’m at loss idk what to do. I don’t want her to stop growing and fall off the chart 😭