I hurt my back at a previous job, manual labour while putting myself though fight school... I've always had a worry that in the long run it may make flying difficult, driving was particularily painful after long periods, so I invested in a backpillow with excellent lumbar support... Well worth the money and the occasional odd glances I get from other pilots. After long cross country flights where I walk away feeling normal, vs. my co-pilot / student / passenger who has a 'normal' back walking away with pain... well its worth the odd glances or comments of 'old man' on occasion.
I would echo the previous suggestions, get your wallet out of your back pocket, go to a back specialist and see what products they recomend for you, find something that fits your particular helicopter and use it for every flight, also invest in a seperate pillow for your car, it will make a huge difference.