Pain in spine--but only with bra??

This has got me confused. I see most people here talking about bras improving back pain.

For me it seems to be the opposite. I usually don't wear one when I stay home most days, and wear them if I have to go into town. I am back pain free on braless days.

But on days that I wear one, within a few hours I get this deep sharp pain in my spine. It feels like it's in one particular vertebrae, if you drew a line between my armpits, it's that level. It tingles and stings. Doesn't feel like muscles aching at all.

I wore one for the past two days and the pain has compounded across both days and I'm in agony.