Thanks So Much, I Have Had A Cough For 3

Thanks so much, I have had a cough for 3 weeks and I am getting out a lot of yellow mucus coming from my nose and throat , I have been using Dristan so I can breath to sleep, Nyquil, cough candies, etc should I be now going to the doctor to get checked, not sure if that would do any good, I keep thinking it is just a cold