How Can Sinus Infections With Swollen Tonsils Be Treated?

Doctor, I m a healthy individual. I m in college, 18, I have no known medical conditions, I run, work out, play lacrosse, eat healthy, take vitamins, wash my hands, bathe regularly, don t drink, don t smoke, everything. Today wraps up the 6th week I ve been sick this school year. Sinus infection after sinus infection, now I have another sinus infection, and my tonsils are the size of golfballs. It s not normal or healthy for someone to be sick this much. All my colds last 2-3 weeks, when it seems like everyone else is only every sick once a year and only for a few days. Do I have some sort of condition? What am I doing wrong? How can I help my immune system?