I have a herniated disc, how much compensation can I expect?

Your question provides limited information. Even if it provided more information, however, it would not be possible or appropriate to give an estimation without an examination of the medical records and the evidence concerning liability. Also, while your post is listed under personal injury, I am wondering if you may have suffered this injury on the job, making it a workers' compensation claim, which would then be impacted by your pay history. In either event, you are best served having an attorney acting in your interest from the earliest possible point in the case. Arrange a consultation. Gather the records you have available. If there was an accident of some sort, if it is possible to do so, photo the scene, vehicles, etc. Do not speak with adjusters without advice of counsel. Continue recommended treatment.