Baby has had a cough & cold for 3 weeks now. I thought it was going & now seems to be back so it could be 2 separate infections who knows. I've taken him to the doctors 3 times just to make sure it hasn't gone to his chest. No temperatures, just a really nasty cough probably caused by all the snot he can't shift. I can't help but think this is going on for a long time. Would I be right or is this normal? He's 15 weeks old.