Yeah, used to happen to me a lot at one time. It's no surprise really as our spine is evolved to be stressed vertically, not horizontally.
The simple solution: don't stay in the one position too long, if you're ever buddied with me you'll notice that during a dive I'll do barrel rolls, or fin on my back or go delibrately inverted etc this is to give my back a bit of a rest from the constant tug of a 12kg weightbelt (for sea diving). Works for me until I get around to making/buying one of those "alphabet" weights for the twinset (note avoiding the discussion on whether it's a P or a D or whatever letter weight
)
HTH
Steve