Continued pain three months after a decompression/fusion should be looked into for source. This would require at least a new MRI and possibly a new CT scan. The possibility of chronic radiculopathy (see website) has to be entertained but this is a diagnosis of exclusion (everything else has to be ruled out before this diagnosis can be made).
Your anterior thigh pain and numbness could originate from the L2 or L3 nerve. This could also be meralgia paresthetica (see website).