I was prescribed topomax 15mg. For a hereditary nervous disorder but have now have a strong low back pain. Have stopped capsules. Is drug cause of pai?

Generally No. But if you are concerned, stop the medicine and see if your back pain improves. If you are on a high dose of topamax, (topiramate) speak with your doctor about reducing the medicine because if you stop cold turkey you could have a seizure.
Maybe. See your doctor about the back pain. Some people get kidney stones on topomax.