Should I still allow my 11 year old sleep in my bed while I sleep in my chair?

It's your home and this has nothing to do with inappropriate boundaries.

If you're more comfortable in the chair due to your back, why does it matter? I would be more focused on why he feels like he cannot sleep in his own room. Usually by 11 most boys are ready to be more independent.

Nope

You put his butt in HIS bed and you make him stay there. Its not healthy to allow him to keep sleeping in your bed. How can he learn to sleep on his own if you keep coddling him?

At 11, he needs to be in his own bed. period.

May I suggest you invest in a hospital bed? I too have sciatica, had 3 back surgeries, etc and once I bought a hospital bed, I was in sleep heaven....the chair is now only on an emergency basis.

that's kind of weird. just make sure you're dressed appropriately if you do so. i would say no my self. he's 11.