Sounds like it might have progressed into Bronchitis or even Walking Pneumonia. Have you been to the doctor?
It very well could be an MS thing, too. Back in April 2005 - right after my parents died (January & March) - I got a terrible case of Bronchitis. And no sooner had I finished my antibiotics and got to feeling a little stronger I got it again! Back to back bouts of it. I've never been so sick in my life. It took several months to regain my strength and get back to somewhat normal. October of 2005 was when I was dx with MS. I believe the Bronchitis infection brought it out of it's remission.
Are you taking anything prescribed for this or just OTC things? I hope you feel better soon. Seems like you've had this cold forever.