Fever, cold. Extreme, making us worried.

My son 17 years is having fever all of a sudden. He has atthma, and prone to cold. most of the days after waking up has blocked nose for couple of hours, sometimes sneezes. But many a time has fever without symptoms of cold. Normally while he is anxious or stressed he has it - that is what we have observed and we believe. 5 years back, suddenly his complexion turned black on a sustained basis. Does not have the glow of a growing up teen ager with normal level of nutrition. He gets tired very soon. Abhors physical work. But regularly plays. He sweats a lot. We have been thinking that it is due to asthma. Since last 3-4 years has only 2/3 bouts of asthma bouts per year. An intelligent boy, and doing well in academics till date. But he is may be more than normal anxiety and nervousness before exams. Commits silly mistakes in exams. Has low energy level. He is apprehensive about things (mostly related to his studies and position) His excitement is a bit extreme, making us worried.