Severe Back Pain

Patient: I am a 21 year old female and I am having severe back pain in my upper and lower back. I have had back pain for years in my upper back between my shoulder blades but it has recently gotten worse. The lower back pain just started about a month ago and has gotten worse since. Doing anything physical even household chores makes the pain worse. My doctor has done a xray, ct scan and bone scan with all of the results coming back normal. What could be causing the pain and why is it getting worse?