Jamie,
I am 7 weeks post fusion at L4-L5. It is very normal for you to have pain as you have and possibly others too! You just had major surgery and like LJ'sWife said.. surgery irritates tissue, bone, and nerves in doing so. Everything is swollen there because of the surgery (which adds pressure to the area). That takes time to heal. The first 3 weeks are the toughest for most at night. What medications are you taking right now? I only got rest about 2-4 hours at a stretch for the first several weeks.
If you are not sleeping at all, I would call your doctor, explain your pain/symptoms and see if there is some medication change/addition you can be perscribed to ease things up for you.
Are you icing your back? If not, you should do so often. I have a coldpack that is flat and flexible.. and I can use it lying down without being bulking like a traditional ice pack. But use whatever you have to get some ice on your back 20 on/off. It helps quite a bit.
Hang in there. It gets better. All of us that have had surgery, front/back/side.. we all know what you are going through. Better days/nights are coming. Take care. Tammy