What Causes Stomach Pain And Constipation At Night?

my question is I have an 11yr old daughter that over the past few years now has had stomach pains which may last up to a few hours mostly at night time she either gets sick or is constipated??
happens after she has had a lot of food in one day: such as toast, bread for lunch, biscuits, chips, dip, pasta and garlic bread for dinner...just a number of carbs for the day and then may not go to the toilet for 4 days ??
I am documenting these episodes but more than likely I will need to take her to a doctor for a consult??