I think wat u got is some sort of exhaustion that ur body cant take it anymore and it signal ur body to rest.

I got this before, when i work in night shift and i train before i head to work. So there is one time, i didnt catch enough sleep during the day time (too hot) and i went to train and i got fever and sick for 3 days and went to doctor, he is asking me if i m working in pub . Then he advice me to go and rest with a 2 days MC

Personally i would say sufficient rest (as in constant sleeping hour) plus micronutrient may somehow do the job. Exercise itself is not suppose to make u sick, u should make u stronger in terms of health, immune system and etc.