I Have Had Trouble Climbing Up Stairs For Over A

I have had trouble climbing up stairs for over a year. To get up I have to pull myself up with the banister. Today my Rheumatologist noticed that I have weakness in my legs and feet. My doctor wants me to go to a Neurologist to find out why I am having this problem. I also have Fibromyalgia and Arthritis. What could be the cause of my problem and what kind of testing will a Neurologist do? I also fall quite often and even if I trip, I wind up falling on the floor. I would appreciate any help that you could give me. Thank you.