What Causes Throbbing In Head In Spite Of Discontinuing Medication?

i m 20 yrs old .i was on venlor xr for last year..now the treatment is ended..sometimes i used suffer from painless throbbing in head and ear ..which is also persistent now (even after stoppage of the medicine)..throbbing is usually occurs when i take sleep less than 6 hrs..lyk 5 hrs..and even 5 and a half hour..is this problem related to the medication? and if it is then why hasnt it subsided after the medicine has stopped?