Over-production of mucus for years. it has never been clear, always thick and yellow. is this chronic sinusitis and what should i do?

Sinusitis: Greetings. Some of your symptoms surely sound like classic chronic sinusitis. The first thing to to try saline nasal irrigation (not just a mist) 3x/day. I also recommend drinking more fluids, consider Motrin as directed and a mucus thinner like mucinex (guaifenesin). See your ENT doctor for a full work up. A ct scan may be recommended as well as a long course of antibiotics with possibly a steroid nose spray.