How can i fix my saxophone with a stuffy sound?

I've played tenor saxophone for almost a year now, but ive played 3 different types of saxophones since 5th grade. Just recently, my tenor has come down with a very stuffy sound, and it is very hard to put air in it. It seems like it is rejecting some of my air. My saxophone is a clic Martin Tenor. It is very old, but an amazing horn nonetheless. any suggestions?