Do you do back strengthening exercises? That might help over time because runners really need endurance in that core area....especially if you have been increasing your miles out for an extended period. Also, there are head, neck and leg pillows that really do help with spine alignment at night. Try slightly elevating your legs and/or adding a cushion between your knees if you are going to rest on your side. Also, consider a good sports chiropractor and scheduling regular massage therapy. The only other suggestion is to add additional doses of Omega 3 (which has natural anti-inflamatory properties).
If you provide a more specific definition of the type and location of the pain, there are many experts in the group that could offer more detailed suggestions.
I agree. Exercises that strengthen the back muscles have pretty much eliminated back pains that I used to get. I still overdue it around home sometimes, but even then the ache is much less. Several that work for me are rows: standing, seated and bent-over; and lat pulldowns. I have weight macines available but there should be free weight equivalents.
Core and lower back exercises should help: Super mans, planks, lots of stuff to do that you do not need any equipment. Core and lower back are very important as we aged and/or mileage goes up it supports everything you do.