How To Ease Constipation And Stop Nose Bleed In Child?

Hi Dr, this is with regards to my 7 yr old son. He has 2 issues. First one, he has been having constipation and difficulty with his stool for a few years, pretty much since he was fully toilet trained at 3.5 yrs. We have been to the Gp a few times, plus a paedritrician twice, and everyone keeps telling us he just needs more fibre in his diet. But i think its more than that, as the stool he does is way bigger than a little kid like him should produce, and he only goes on average every 5-7 days, even up to 10 days when really bad. He eats a fair amount of fruit and vegie and drinks about 6-7 cups of watered down juice and milk each day. Second problem, he seems to have nose bleeds quite easily, has had 2 in the last 24 hrs. I was wondering if there is something that can be done to stop this ? Thank you, Sharon