Lumbar radiculopathy: dr says I don't have disk problems, I've not had an injury to my back, so what else could cause that? Is it permenant?

Sciatica. Pain in the distribution as you suggested describes the pattern of the nerve that travels in the leg called the sciatic nerve. The sciatic nerve is not the cause of the pain source, it is the result of an irritated nerve typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease requiring further evaluation by a spine specialist.
See spine specialist. Must have an MRI to determine disk health. Other causes of pain down the leg: 1) piriformis syndrome with sciatica 2) lumbar facet joints (referred pain) 3) sacroiliac joint (referred) 4) myofascial trigger points 5) spinal stenosis with neurogenic claudication 6) vascular claudication may need emg/ncs.
Multiple causes. Degenerative disc disease can cause symptoms. Mri could reveal pinched nerves if pain and weakness become severe. If steroids are used for asthma could have osteoporosis and compression fractures. Lab work could determine inflammatory causes. Emg could define type of nerve involvement. Recent birth could result in si joint or pubic pain. Conservative therapy with nsaids, rest or epidurals help.