I'm getting sick quite often and symptoms are the same.

I live a healthy life. I eat healthy food and do sports when it's possible and I never smoked. But ever since 3th grade I started to get sick very often Almost every month since 8th grade I cough often and feel pain in my chest. It lasts about a week. We thought I may have something wrong with my lungs, but we didn't find anything at all. I've been tested many times but still no results. My mother says it should be gone soon but I don't think so. Even now I'm coughing and my lungs hurt. What do you think?
I'm getting sick quite often and symptoms are the same.
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