I'm having mid-back pain. Right side only. Had three ultrasounds, Hydrascan, and bloodwork-all fine. Help!?

I have been having back pain for over a year now. On occasion it is also in my abdomen same area just in the front. Most often, however, it is in my mid back on the right side-never left side. Sometimes it is dull and other times it is sharp. It is definitely internal-doesn't feel like ribs. I thought it was my gallbladder because I was also having some right shoulder pain and muscle spasms, but haven't had any problems with that in quite sometime. My doctor has done three ultrasounds-one internal, hydrascan, and tons of bloodwork-all results/tests were normal. The pain will disappear and reappear periodically. It is incredibly frustrating and painful, any suggestions. 26-female-healthy other than this.