Putting in so much effort at work has resulted in an overtired mind and body. You seldom if ever give any regard to your health and this is the reason for the many health problems that seem to bother you from time to time. No, you do not have a weak immune system; it is you who is pushing your body to the extreme. So, stop blaming your immunity and give some thought to the many atrocities you subject your body to. A sound mind resides in a sound body, so take heed and stop taking your health for granted.