My 17 month old has a really bad cough and fever, not acting himself either. What could this be?

Could be viral. Usually it is a virus that causes cough and fever, but it can often be bacterial. If he does not improve with tylenol (acetaminophen) or ibuprofen, call your pediatrician or go to the nearest emergency room if your child had trouble breathing.
Cold or more serious. How long has your child been sick? Most colds include fever, runnynose, being grumpy and cough. Is your child grumpy or sleepy. Lethargy could be a more serious symptom and may warrant seeing your doctor sooner than later. And as far as the cough, is this causing difficulty in breathing, if so, your child should be seen by a doctor.