Truly sorry you have to deal with this. I'm on 4 years, and it has been truly horrible. I've had 2 minimally invasive discectomies, and 1 surgery for Spinal Cord Stimulator implant, all unsuccessful. All surgeries were done after 2 years of physical therapists, epidurals, osteopaths, etc. It was recently discovered that my L4-5 disc that exhibited a small bulge on MRI is actually badly torn. I'm having fusion surgery Tuesday and will hope for the best.
The usual accepted protocol is 6 months of conservative therapy (P/T, NSAIDS, shots, rest, etc.) before you consider surgery. I'm assuming you've had an MRI since you've been diagnosed with specific degenerative disc problems. L4-5 is usually the culprit, but occassionallly L5-S1 or, even more rarely, L3-4. I would HIGHLY encourage you to have all diagnostic tests possible to define exactly what your pain generator is, and definitely would ask for an EMG, which not only can help locate the problem, but determine if you have any nerve damage or compression. If so, then in my non-professional opinion, you would likely need surgery to relieve the compression, which could entail disc removal and fusion, or maybe just an out-patient micro-discectomy to trim the bulging disc. I wouldn't do the epidural again since you didn't get any real relief, but you might request a Nerve Root block, which is a similar procedure but directed at a specific nerve root space. This can provide some lasting relief, and would help diagnose the problem. Some surgeons/doctors don't like it, but a Provocative Discography can provide pretty definitive diagnosis. This involves injecting the discs with dye/fluid in an effort to reproduce your pain. If it does, it obviously will not be pleasant. The dye aids in visualization when they do a CT scan afterwards. It took this to finally diagnose my torn disc. Pain was not reproduced, however, as it was so badly torn it wouldn't hold fluid and "inflate", which causes the nerve compression and associated pain.
As to your original question, pretty much nothing has ever given me relief. I do take OxyContin, which helps, but many days are still miserable. Pain killers just don't seem to work very well on this type of nerve-related pain. They help, but they can't kill it, at least not for me. So, I take only what I must to make it bearable and still stay coherent. I wish I could tell you something that might help more, but I haven't found it.
My last advice is to seek out the very best spine specialists you can find. Travel if you must, and if it's possible for you. I'm fortunate that my insurance covers pretty much nationwide, so there's a lot of preferred providers. However, it has taken me 4 years to find the right doctors, and they're a 3 hour drive away. I live in a major metro area loaded with supposedly highly-competent doctors, and was referred to supposedly the best available, but have been unsuccessful in getting the correct care for my problem. I truly wish you the best. Sciatica is a terrible, burning pain, and difficult for others to understand because you don't really see the affliction. Hang in there. Good luck and God Bless.