Does anyone remember me talking about constipation in my daughter?

Does anyone remember me talking about constipation in my daughter? The pediatrician prescribed Friskio formula earlier, which didn't help and even worsened things. Recently, she had another appointment, surprised that it didn't work, and was advised to buy lactose-free formula. I bought Nutrilac lactose-free. But the doctor didn't clarify anything, and I forgot to ask... How do you introduce Nutrilac lactose-free? When should it be given? Currently, only at night, both morning and night. Should I replace one feeding? Or not so often? Or everything? Constipation is terrible... She eats well, eats vegetables and porridge, different food. Blackcurrant, Biolacta, all eats. Doesn't drink