Rotary wing aircraft and back problems do seem to be linked more frequently than can be explained by random chance. Vibration may be one cause but you also seem to be using all your limbs constantly just to stay up in the air, unlike fixed wing aircraft which can allow some degree of relaxation. Just my opinion.
Over the counter pain medication can help, but can also seriously mess with your flying abilities if you are susceptible to some ingredients. Equivalent to the performance reduction you get from a hangover but without the headache.