HEAVY feeling in chest/throat?

almost like its full of mucus or something....feels like right after u smoke, or while doing it, it feels heavy, at least for me...however, i RARELY smoke, when i do, VERY little...only like half a cig...but i havent smoked in ages...i dont understand...could it be the smog? i live in atlanta, super hot and smog...never had this prob b4 tho...help?