I can understand how your symptoms could cause you to feel some anxiety, and it's true that anxiety can manifest itself in just about any physical aspect you can imagine. But I think in your case, you need to have a doctor rule out an organic reason for these symptoms. I am most certainly not telling you to lie to your doctor, but perhaps the first words out of your mouth shouldn't be "Doctor, I'm very anxious..........." Those words, far too often, make it too easy for the doctor to blame ALL your symptoms on anxiety, send you home with some "calming tablets," and file your chart away.
Since you had problems with your abdomen, which is now causing pain in your lower back, BEFORE you began to feel anxious about it, let that tell you something.
Don't be afraid to speak up. You deserve the best medical care you can get.
I hope you'll let us know what you find out.
Peace
Greenlydia