Cheryl, sounds like you have been enduring this cold for too long. I agree with tkrik, try to get a culture, perhaps from an ENT.

Could your immune system be compromised from what you might be taking in the study?

I can get super bad colds and bronchitis from working with teenagers, so as soon as I see any evidence of yellow or green, I get on an antibiotic that day!!

Hope you feel better soon, otherwise I agree with NurseNancy.