Why do i get a constant cough without having the flu ?

Very common: Top three reasons for cough are, asthma, post nasal drip (allergic rhinitis) or gastro-esophageal reflux. If youre taking a blood pressure pill in the ace inhibitor class, that can also cause cough!

Many causes: Allergies and post nasal drip could be the cause. You could have a more silent case of asthma too! there are other infections that cause cough that don't have flu like symptoms. Walking pneumonia is like this (chlamydia infection). A low grade pertussis (whooping cough) could cause this. When was your last DPT booster? I'd get it checked out. May be simple, may be complex? Get seen.

Of course: The flu is one of the least common causes of cough. The more common causes include asthma, rhino sinusitis and reflux, together account for more than 90% of chronic cough.

Possibilities...: The possibilities for a cough lasting 3 weeks or longer include bronchospasm of any etiology, gerd, post-nasal drip or any combination of these factors. The treatment of each of these is different so see you doctor so the diagnosis in your case can be made and the proper treatment rendered. Good luck!