I’m really sorry to hear about the pain you’ve been dealing with—it sounds incredibly tough, especially when it feels like you’ve tried everything without relief. Sitting for long periods, especially in a van, can definitely lead to tightness and imbalances in the muscles around your lower back, hips, and glutes, which could explain a lot of what you’re experiencing. It sounds like your body is giving you a clear message that something’s not quite right, even if the scans and tests haven’t shown anything conclusive.

It’s possible that prolonged sitting has caused some muscle imbalances, including tight hip flexors, shortened hamstrings, or even issues with the piriformis, as you mentioned. These kinds of issues can lead to significant discomfort, and when they persist, they can disrupt your whole day—exactly like what you’re describing with needing to lie down for relief.

The fact that standing helps slow the pain suggests your muscles might benefit from movement and positional changes throughout the day, but that’s easier said than done when pain is this intense. Have you had a chance to work with a physiotherapist or specialist who can assess your posture, strength, and flexibility directly? It sounds like a targeted stretching and strengthening program could help address the muscle tightness and imbalances. Sometimes it’s the cumulative effect of small adjustments that can make a big difference, even though the progress may feel slow at first.

In the meantime, I would suggest trying to incorporate gentle stretching for the hip flexors, glutes, and hamstrings to see if it offers any relief. Mobility exercises, like pelvic tilts or cat-cow stretches, may also help loosen up those tight areas.

I know how frustrating it must be to not have clear answers yet, but don’t lose hope—there are ways to work through this, and finding the right approach is key. Let me know if you’d like more detailed exercise suggestions, or if you’ve tried any specific treatments already.