Infant Heat Rash

My son is 5 weeks old and for the past week and a half, a rash that initially developed on his head is progressively worsening and is moving downward on his body.  The rash is quite red with some raised areas and white centers.  Although he is running a slightly elevated temperature (99.0) and seems that his body is warmer to the touch than usual, he has no other remarkable symptoms.  I've done some looking up on the internet and the only conclusion that I can come to is heat rash, but I've followed the guidelines to reduce the rash (such as dressing in light, cotton clothing, and removing heavy blankets at night), and it does not appear to get any better.  Is this something I should be concerned about/go to the doctor for?

[MomofTwo83]

My daughter has the same thing.  She was born on 4-12-08 and started about a week and a half ago.  It is still moving downward on her body.  Don't know what it is.  No other symptoms of anything.  Did you ever get an answer?