Suggest Treatment For Sore Throat And Low Grade Fever

i am fourteen year old girl, and about 3 weeks ago, i started having a really sore throat with no mucus, but i had low fever for a couple days. then, the fever stopped, but the cough worsened and i started coughing up yellow mucus, which often made me gag and panick because it blocked my airway for a couple seconds. Since then, the cough comes and goes and i m still coughing up yellow mucus, but i don t have any fever. i took my respiratory rate, and i took 28 breaths per minute when the normal rate is 12 to 16 breaths per minute. Should i go to the doctor? What do you think it is? If i don t have fever, it can t be serious like bronchitis or pneumonia, right?