19mt old son with bad head cold, bad cough and a spotty rash on his back!!!?

he has had the head cold now since saturday and was gettin better, when a rash started spreading on his back, i brought him to a&e yesterday to get the rash looked at and the doc said it was just his bodies reaction to his head cold and it was nothing to worry about that i would eventually fade, now today he has a really bad cough and the head cold is returning, i am at a dead end with what to do, as the doc just told me to keep doin what im doin with him, iv been giving him panadol baby as its the only thing his belly will allow, he pucks up everything else, i feel helpless as its the worst head cold he has ever had, he is drinking and eating plenty and is in great form for themost part of the day but when he starts coughing its like a chain reaction with watery eyes, runny nose and generally just him being upset,,,, do any mums have any tips on what worked for them?? shud i be worried about the rash if the doc says its ok?