I take imipramine 4 pain but it makes me fall asleep, will this symptom go away after a couple weeks ?

Probably not: Although Imipramine has been shown to be quite helpful, it's use is usually limited to night-time use due to sedation, and this effect usually doesn't get much better. Many people find that a single dose before bed helps with sleep and still helps with the pain during the day....Even after the sedation wears off.

Likely yes: It is likely that the sedation will improve with time.