I always have phlegm in my throat, what can cause this?

As you know phlegm is thick secretions. There are several causes....post nasal drip, milk/dairy products, sinus infection and many more. Try running a humidifier 24/7 in your room. especially at night. See if this helps loosen up the thickness of the mucous/phlegm. If condition persists, a visit to the doctor may help...it wouldn't hurt to have an exam or xray of your sinuses/head. They just might find something simple or nothing at all. Good luck :O)