Warning, I have no clue what I'm talking about, just trying to help:
Try just going to a doctor, not necessarily a hospital, just call into a local one and ask for an appointment for a checkup or something. Complain about backpains, they'd run tests, then hopefully tell you what the problem is. Going from there would be up to you.
Whatever you do though, I'd make sure to do it quickly. In your line of work, a potentially severe back problem isn't going to get any better.