My head is so heavy,my voice has changed,I feel a little numb at times and drowzy too.What can be the cause?

Um, it's cold/flu season... I'd see a doctor if I were you.
Other than that, I don't believe that the internet is a place for diagnoses.
If you just want something soothing, try some hot tea, with lemon and honey, not sugar (assuming there are no allergies), and rest as much as you can.
Hope you feel better