FTM-Please Help! Baby Rash or Acne!!

So my son 5 weeks old, born at 37weeks. And he just started breaking out and It seems to be spreading. he also seems to be a little congested and I think he might be getting a cold :( his temp is 99.2 (which is fine?) and he has been eating normal amounts. Could the two possibly even be related to him being sick? The rash started a few days before his cold! Also I read that could be an allergy to his formula? Idk what do you guys think? I have an appt tomorrow but it would be nice to have some input before then! Thank you so much in advance!!