Walk, walk, walk and build up those core muscle through a gentle exercise and stretching program. Start out slow and work your way up to a comfortable place. Back exercises are for life. If we let our backs go, then we end up in surgery or pain.
Desk jobs are as bad on the back as heavy lifting, maybe more so because we let our backs go. There are lots of exercises and stretches that can be done while taking a break, in your office chair.
If you take a ten minute break every hour, or every few hours and go outside and walk, it makes a world of difference.
I hope that you find some relief,