What type of surgery did you have?
It is possible that you may have reherniated the disc, or one at an adjacent level. Or, it is possible that your body is still responding from the what it went through during surgery. If a nerve was compressed, it can take a very long time to heal -- 2 years is not uncommon.
You might ask your surgeon about taking Lyrica or Neurontin for the nerve pain. It helps some people quite a lot. Have you talked with your PT and explained that you have more pain than a month ago? Perhaps something you're doing in therapy is aggravating the situation.
Unfortunately all the post-surgery stuff seems to be done by trial and error. "Let's try this and see if it helps..."