Suggest Treatment For Pain Above Buttocks That Radiates To Legs

Question: I'm 51 years old male and I get pain in the mornings when I get up from bed and stand which eventually eases up during the course of the day by normal activity. The pain starts from right hand side just above the buttocks which initiates and slowly radiates towards the right leg and the pain is not continuous and it is more on and off. I already had a right leg foot drop at the age of 40 from which I could recover well on time and the next 11 years, I could do my normal work. My recent MRI findings taken at end 2013 shows mild disc herniations at L3-L4,L4-L5 and grade 1 spondylolisthes at L5-S at my lumbar section of the spine. Presently I have not gone for a scan just because of the pain takes place only in the mornings for short time and I'm comfortable without pain for the rest of the day. This pain started about a month ago when I was playing badminton with stretching too much while playing but without any warming up exercises prior playing. Consulted a physician who is qualified as M.D. (PMR) suggested that this could be piriformis syndrome and he started treating with bio flex laser therapy which eventually doesn't give solution as the pain comes as usual in the mornings and he is suggesting if not by this,then he says he will put me on an therapy called IDD (intervertebral differential dynamics) for the disc herniations problem which I have from before but also he is little hesitant to carry out this since I have a grade 1 spondylolisthesis at L5-S. I'm totally confused and please help me out whether to go for an MRI or any other scan which can find out the exact problem as I also myself suspect whether this could be sacriloiliac joint syndrome or sciatica due to disc herniations. Kindly give me a solution.

Will you please clarify as the answer is disc bulge may aggravate due to therapy.is it the right therapy to go for or what do you suggest? I will do mri with si joint scan.