My sixteen year old son has had cold symptoms .his headache and stomach ache have gone away but he gets tons of mucus in morning and night. ?

Not uncommon: It's not unusual to have more congestion and mucus at night, as a result of laying flat. This could be related to the common cold or other upper respiratory viral infection or drainage from the sinuses. Most viral infections, including sinus infections, resolve within 5-7 days and don't require antibiotics. If it's been longer than that, your son should see his doctor.