Suggest Medication For Chronic Cough And Chest Congestion

My 8 month-old son has had a nasty cold for over two weeks now. He had a cough that was wet and mucousy, now it s turned dry and he wheezes when he exhales. He also cries every time he coughs (like it hurts him) and it s waking him up multiple times a night and during naptime. What can/should I do for him to help soothe his cough?