advice needed for 6y/o

Hi,
I have a six y/o son who has problems with some form of blockage. He doesnt breath through his nose only the mouth and he talks very "gobby" which is the only word I can think of that describes it.He has already had a few bouts of tonsillitis.I took him to the doctors and they gave me antihistimenes and piriton. I dont give him them, I dont want him to start all that at his age.He sometimes wakes in the night crying and I am starting to wonder if he has some problem breathing.When I tell him to close his mouth and breath through his nose he cannot do it.He does not have a cold.He has a poor appiteite and is generally quite weak when it comes to fighting illness.He mirrors me when it comes to his throat problems. My adenoids are gone I had them taken out when I was young,but I still have alot of throat problems.
I hope this does not have to happen to him.He takes the poor appiteite and weak imune from my husband.It seems that he has got both our weaknesses.
I would be so grateful for any advice.