Let me summarize your history and complaints. 5 months ago you were lifting boxes and felt and heard a click or pop type sound from your midback (I assume the area in between the bottom of your shoulder blades). This pain disappeared and three weeks later the same pain reappeared with lifting again. Pain also occurred in both arms and legs.
You rested for two months without improvement and then saw a chiropractor. He or she treated you without relief and obtained an MRI that noted a small herniated disc at T7-8 that slightly compresses the cord or at least distorts the cord pathway.
Your arm symptoms improved but your leg symptoms are just as significant as at onset of initial pain. You have no weakness. Your thoracic pain is a 7-8 on a VAS scale and the pain does not radiate around the ribs. I imagine you have no bowel or bladder symptoms and have no imbalance. The leg pain is less than your thoracic pain and is bilateral with left leg more intense.
First off- if the thoracic disc herniation is causing your thoracic pain and is not causing cord compression (you report no myelopathy- see web site), continue non-surgical treatment. Surgically treating thoracic disc herniations is difficult and can cause symptoms that were not present previously. Epidural injections can be helpful and occasionally, the facets can cause local pain. Facet blocks and rhizotomies (see web site) can be helpful.
Your leg pain is most likely not originating from the thoracic spine. You indicate that you have no lower back pain but there are circumstances that nerve compression may not be associated with back pain. If you underwent a thorough physical examination, was there any evidence of nerve root pathology?
It would be unusual to have onset of a thoracic disc herniation and onset of a lumbar disc herniation at the same time, especially a lumbar herniation that caused compression of both sides but stranger things have happened. You could have a systemic neurological problem and a neurological consult may be in order.
Another set of eyes may be helpful to determine what disorder is causing your symptoms.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.