D.R.
At only 3 weeks old a trip to the doctor is probably best. I'll tell you why I had no trouble running to the doctor with my infants. A friends child got a cold and the mother had it too. Neither went to the doctor b/c it was just a cold, but the mom got better and the baby got worse. By the time they went to the emergency room it was too late for the baby and she died of pneumonia at 11 days old. PLEASE go to the doctor.