Reclined sitting and back pain - anyone else dealing with this?

I spend like 3-4 hours a day reclined on the couch feeding or burping our 6 week old. My lower back is absolutely destroyed. I've tried adjusting positions but honestly when you're that tired, form goes out the window. Using a heating pad at night which helps a bit but I'm concerned about this becoming a chronic thing. Any dads here got solutions? Specific pillow recommendations? Better posture tips that don't require me to suddenly become flexible?