I am going into my 4th week post op as well. Still taking pain meds AND sleeping pills. I am having difficulty sleeping(the most at once is 2 to 3 hours), but I am also having alot of difficulty with recovery.
I do know from past medical issues involving pain meds that it is normal to not sleep after you quit taking them(withdrawal symptoms). Your body will get back into it's own sleeping patterns soon enough. Hope this helped.