Long-lasting cough

Patient: Hello,I’ve had an insanely horrible cough since mid-November. Around the 20th of December, I was hit with a full-on cold that left me with the common symptoms as well as my cough and a loss of appetite – no fever though. It remained as a common-cold until the 28th or so, and then I just had my cough and a sore throat. Around New Years day, I felt very harsh sinus headaches, stuffiness in the nose, coughs, and it was very hard for me to speak, so I went to the clinic and the doctor told me that I had a very severe sinus infection and he prescribed amoxicillin for the week and a nasal decongestant that I have been using since prescribed. My sinus headaches are less sever these last few days, but I’m still incredibly tired, have a very deep chest cough, and oddly, I’m dizzy. I do not know why I’ve been sick for so long and I’m worried it may be something severe. I’m a vocalist, so my voice is very important to me, and I’d hate to lose it, but it hasn’t been 100% since mid-November. I, myself haven’t been 100% since November as well. Help me, please.

Symptoms: coughing, sneezing, headaches, hard to sleep, dizziness, sore throat, mucus and phlegm