I was pouring concrete last year pulled something in back. went to chiropractic. never missed work. hurt back recently now mri says herniated disc

Florida has some specific laws regarding pre-existing problems that are also work related and how they affect your new accident assuming your new accident is covered by workers' compensation.  Your earlier accident where you went to a chiropractor would have to be covered as a work-related accident in order for you to fit under these specific laws.  If the earlier event was never covered under workers' compensation, it can be treated as a pre-existing condition to reduce or completely stop your benefits from your new accident so there are a lot of facts that a lawyer would need in order to answer your question better.