My peronsal theory is that you've been sleeping good since your surgery because of the pain meds. and not dealing with the old pain. Now that you're past the initial surgery pain and not needing the pain meds. like you did, your body is kind of going through withdrawl of the meds. If you're still taking naps during the day like I did before I went back to work, you're probably just not as sleepy at night because of them. Maybe back off of the daytime naps if your taking them. Also, the allergy tabs (over-the-counter antihistimines like Benadryl or store brand) like mentioned above could help. You could also take a look on-line for some home remedies for insomnia. Right now I'm having the opposite problem, I am so tired and sleepy, I can't get enough sleep! Good luck!