Re: Always sick it seems!
Well, first the standard disclaimer: consult your physician for a thorough physical exam and history.
Second, if you are really training hard, you are stressing your body. One of the markers of the stress response is higher secretion of cortisol from the adrenal glands. Cortisol's actions in the body include: muscle catabolism (breakdown of muscle), elevation of blood sugar, shift to fat storage, especially in the abdomen and across the back, and lowered immunity to infection.
This a sometimes a sign of overtraining. Other signs of overtraining include increased morning heart rate, decreased athletic performance, poor sleep, mood changes including depression and decreased enthusiasm for exercise, slower recovery--heart rate takes longer to go down after a workout.
Sleep---good, restorative sleep---is critical when training hard. You can be marginally ill, physiologically speaking, when you are really pushing the boundaries, and that's when that sleep becomes important.
Could you be overtraining?