I have serious lower back pain. Had an MRI and it showed retro lethesis of the L4/L5 region and a 3mmm bugling disk in the L2/L3 region.?

See a pain doctor. Fortunately, most cases of lower back pain do get better with a appropriate treatment plan. I would advise you to consult with your primary care doctor first to see if you need to see a spine surgeon or a pain specialist.
Two reasons for pain. are included in your description. The disc bulge at L2-3 could compress nerves in the central canal or in the small neural foramina where the nerves exit. Retrolisthesis is when a vertebral body moves backwards with relation to the bone below it. This can also pinch the nerves in the central canal or neural foramina. You could see a spine surgeon, or go nonsurgical with physical therapy.