I'm waiting on a discectomy for prolonged disc problems. I've had 3 epidural inj in past 4 mo. What's the best prescription to control mod-sev consistent pain?

Depends . . . The best treatment for any condition is one that you can afford, are willing to take, has minimal side effects, and solves your condition. For moderate to severe pain, there are many narcotic or opioid options available, both fast acting & long acting. You'll want a combination of the two to avoid a roller coaster effect of side effects from too much and pain from not enough. Go see your familymd.
Many things can help. The nerve pain is typically best treated with meds called antineuropathics. Neurontin (gabapentin) / Gabapentin is most commonly used. Besides medications prescribed by your doctor try to keep you activity and movement as normal as possible. This is hard to do but bery helpful. The surgery should help with the leg pain, it may do nothing for the back pain.