The Goldilocks Effect (need advice!)

I am an early-thirties, work-from-home male who spends a lot of his time either hunched over a desk (as ergonomically as possible) or watching television (part of the gig). The sofa we had recently reduced itself it mush. I could tell because my lower back and shoulders, part of the complex of issues brought on by bad posture, immobility, and repetitive motion, were flaring up like crazy. I figured I would go in the opposite direction, and bought a beautiful turn-of-the-century sofa that feels like it was constructed out of baseball bats. Cushioning still perfectly firm.

The problem is ... this one causes me pain, too, if I sit in it for over thirty minutes. Maybe the trick is to get up and stretch. But long-term, I am wondering if there's any way around this predicament, or I'm just going to have to live with it or buy a second couch for more involved viewing.

I have also lately been trying to build up my back through more exercise and weights. Can't tell if this is helping or exacerbating the soreness.

Is there some simply configuration of pillows that might make this new couch more friendly?

Thanks!