Do i have allergies, cold or flu? i have a lot of nasal congestion and a tiny headache but i've taken tylenol (acetaminophen) about 3 minutes ago but it hasn't kicked in.

Decongestant: Tylenol (acetaminophen) might help your pain but would not help the congestion. Try taking a decongestant (pseudophedrine) and anti-histamine (benadryl or claritin) if you also have a runny nose. Try using a saline nasal spray or a humidifier at home.

Fever?: The best way to tell allergies vs infection is fever - allergies don't cause fever. Viral infections shouldn't last more than a week or two- if your symptoms last longer than that, see your physician to help sort it out.