Is the phlegm I am coughing up coming from my throat or lungs?

I have a cold and a really bad cough. Sometimes it feels like I'm choking and I don't feel better until I cough up some phlegm. Sometimes I can't cough up the phlegm so just keep coughing. My lungs feel heavy, so I always umed I was coughing UP phlegm from them but my boyfriend says I'm coughing it up from my throat and it's post nasal drip going down the back of it. Which of us is right?