That is a great question and one that is best answered by your primary care doctor
or a physician specializing in the treatment of back pain such as a medical spine doctor. There are several causes for what you have described, but it is difficult to know the exact cause of your symptoms because of the limited history provided (it is unclear your age, gender, and comorbidities, which are all very important in diagnosing the condition). For this reason, it is best that you see a doctor who can answer these questions. In general, as we age, we have degenerative changes to our spines which are related to normal wear and tear and as these progress, they can cause compression on the nerves or spinal cord itself. When you yawn or take a deep breath, or cough or bear down, you can sometimes exacerbate these changes in your low back which can manifest itself by a feeling of low back pain. You can try symptomatic alleviation by taking NSAIDs, stretching, low back strengthening exercises, losing weight and stopping smoking. Only a doctor can tell you the cause and offer treatment options and so it is recommended that you see one to discuss this concern.