Took My 6 Year Old To Doctor Last Week(Wednesday Morning)

Took my 6 year old to Doctor last week(Wednesday morning) He complained of dizziness, loss of appetite and had a fever since Tuesday afternoon. They tested for flu and strep and both were negative. Doctor said it was prob viral and could take 1-5 days to run its course. He intermittently runs a fever...most of the time in late afternoon and now has developed a cough. He is normally a BIG eater and barely eats and is weak. Color comes and goes...just perplexed. Wondered since its been a week since it started if I should take him back?