5 month old with thick mucus?

My son has very thick mucus. He has seen many doctors and they all say keep doing what I'm doing. I am starting to become upset because what Im doing isnt helping. He sounds really congested. I have tried the Humidifier(cool-mist), nose suction, saline drops, and hot steam shower. When I do get one or two lil boogers there are white and so sticky and thick, I cant imagine it all coming up without real help.I can hear it in his chest sometimes.....please advice?