[Sirena]

She is 2 years and 5 months old. And I am thinking of giving her this because she is not eating very well lately. She is very skinny but she has a belly, she looks pale and when she is hungry she only wants to drink juice or milk. the doctor says she is ok because she is 26 pounds and that is ok with the grow chart or whatever. And he said that if my girl is not itching on her bottom, then there are no pinworms. She got a radiography of her stomach yesterday and this morning the nurse called me and said she's just constipated, and that I should give her milk of magnesia, but she did not say how much or for how long, but the guy at the farmacy said give her 1 to 3 tsp. for this day only.
Any similar cases out there? Please help, should I do something else? I want my girl to look healthier or a little bit more chunky, I'm worried about her.