cough

ive had a cough for about 3 months.  when it first started i didnt feel sick at all, other than a cough, i felt fine.  when i do cough, yellowish white mucus comes up.  a few weeks after the cold started my throat started hurting and i was diagnosed with mono, and possibly tonsilitis.  a few days into taking antibiotics i got much, much better.  i havent felt sick at all since, but i still have the cough.  im coughing up less than i used to be, and its clearer than before, but it isnt going away.  any ideas of what it could be, or what i can do to get rid of it?? thanks.