Sounds like you and your son may have a lung or bronchial infection or an allergic reaction to something in your home environment. Nasal irrigation may help with the sinus and nasal secretions, but after 3 months, both of you should have a chest x-ray, a blood count and examination of any mucus you may raise. With 3 months of chest congestion, you may have to see a lung specialist to get an answer.
I'm afraid things would happen like this, if it's mucus i think u should take something to make your stumach acid destroy it faster or have it sucked out, eitheier that or you might die early...