constipation in premature baby

Hi,

My baby is 10months old, she was born in the 34th week, c-sec. since her birth she is facing the problem of constipation on and off. (she has been on formula milk ever since her birth except a few months of mother's milk but that too in a very inadequate qyt.) Since last two weeks it has become worse. she is passing rock hard stools after hours of straining and crying. The doc prescribed her duphalac some months back which helped initially but not anymore...she was prescribed to be given 5ml twice a day but when i give it now she gets a vomiting and a lesser dose of 2ml or so aint helping so as the last remedy i have to give her supository which the chemist says shouldnt be made a habit.

I have checked out the earlier posts regarding infant constipation and I am totally confused what to give her?? I have bryonia D6, C30 and Nux Vomica C30 at home...kindly suggest what can be given to her to relieve her painful situation permanently.

Also i think one main reason causing this is her lack of water, milk and food intake. she is terribly stubborn in eating or drinking anything that will help her relieve of this problem...she wont take prunes, or its juice, apples or juice, pappaya, water etc... :(( if i try forcefully she cries till she sweats from her head like i have poured a full glass of water on her head!!

Thanks in advance,
Manisha