My daughter had issues with breathing since she was born. She was constantly congested, breathing issues and dark circles under her eyes indicating she wasn't sleeping well. My doc suggested an pediatric allergist to rule out any allergies. Since he found no allergies, he, the allergist, suggested an x-ray of adenoids and a trip to the ENT. Finally, we found that it was her adenoids!!! They were so enlarged it was restricting her breathing. We had the adenoids removed and tubes put in her ears. I can happily say it's been 3.5 years since then and she hasn't had anymore breathing problems and has had maybe 2 "colds' since then.
Good Luck! T.