I Am Experiencing On And Off Cold Symptoms, I Feel

I am experiencing on and off cold symptoms, I feel great for a few days then feel like im coming down w a cold...runny nose, slight sore throat malaise, chills...it never blossoms into a cold, goes away after a few days or even hours.. then I feel great again. Has been going on all winter...since November....now its back again! I eat right, get exercise and enough rest, drink plenty of fluids and take vitamins. I am currently using Zinc with these symptoms. Thank you