My friends son got weird stomach, what is it???

my friends little boy is 7 and his digestive system is not right. He doesnt pooh properly so he on sachets of laxative, this doesnt seem to be working. His diet is rubbish, lots of junk food. Now all of a sudden he started bringing up acid/bile and is sometimes sick with bile. He looks unhealthy to me, his cheeks are like bloated, as though he beeen blown up!! Wot is this???