Too much sport without proper nutrition weakens your immune system and that is why you get all these infections...
Before exercising, get a carbohydrate meal because that will fuel your activities and after your work-out have a salad,protein and some carbohydrates too to replace the lost glycogen during the work-out.
For you to have a structured nutrition plan, it is necessary to know what weight and height you are,your BMI,distribution of fat(to decide what to do about carbohydrates),your energy expenditure(how much execse you do and how often) and energy intake.I suspect that your energy intake maybe not enough or maybe your meals are not balanced or the wrong type for the particular time of the day.