My DS is about to turn 6 and he has always had problems with his nose and congestion. He is a mouth breather and cannot eat/drink/move around without grunting and groaning because there is so little air movement through his nose so his mouth is always wide open.
I took him to the GP who referred him to ENT after 6 months waiting for the appointment the Dr said there is air moving (she held a metal thing up to his nose and asked him to blow out of his nostrils as hard as he could) and it showed there is movement so it's not a medical issue and that was it.
They tested his ears and said one side the tube that goes from ear to nose is under developed but that it will catch up as he grows.
She then suggested twice daily sinus rinses with Sterimar which we've been doing but it's had no effect.
Other children have noticed and had commented that they don't want to sit with DS at lunch because he makes so much noise when eating. 
He sleeps poorly because he constantly seems to be gasping for air in his sleep and he wakes up with a sore throat.
He's had multiple ear and throat infection every ear since he was a baby, he had severe RSV and bronchitis when he was 6weeks old and was in hospital for weeks on O2 being NG fed so I don't know if it's off the back of that.
I'm not sure what else to do though or if I can help in anyway? I don't want him to become a social outcast because he's such a noisy breather and eater and I want him to be able to exercise in comfort and not constantly be sniffing and grunting all the time. 