I’d work to get a definitive answer from your chiropractor or health care provider. If it persists, you want to make sure first and foremost that you have the proper diagnosis. Your chiro should be giving you some exercises to do that are specific to your need. Shouldn’t be a need to throw the kitchen sink at it and hope something works. There’s a host of issues that can contribute to it, not just the long hours in the truck. You might not be able to change much about the traveling but you should have some form of control for what you do outside the job. Make sure you’re performing all movements with good technique to insure that nothing inside the gym is contributing to the problem but helping to alleviate the issues.
I would suggest picking up the lumbar back aid that PRS sells. Found here:
https://www.powerrackstrength.com/product/lumbair-back-pad/
This can help to insure that you are maintaining the best possible posture during those times when it would be the most difficult.
Talk to your chiro to make sure you’re getting the maximum benefit from him. Muscle moves bone, bone doesn’t move muscle so there needs to be some kind of corrective work he has you doing.
I know this is kind of an open answer but none of us are doctors or PTs, so it’s tough (even if we were) to give a more appropriate response without knowing more details about your lifting, time dealing with the injury/pain, and severity.
Best of luck and hope this helps at least a little.
Will.