I love my pedometer... but I too had problems with getting them to work right until I bought the Omron HJ-112. Wow I love the thing!!
One good way to use the ped -- if you have one such as this which also counts aerobic steps -- is to keep track of those too. For example today I had 14,055 total steps (I get a lot of steps at work) BUT 7,187 of them were aerobic, for a total of 63 minutes... or averaging 114 steps per minute (anything 60 or over for at least 10 minutes is aerobic). It is fun to challenge myself and try to break my records, etc.
Walking is GREAT exercise... sure it is good if we can do other stuff too but hey if not just do what you CAN do and don't "fret" about what you can't. Until recently walking was pretty much all I was doing except using some workout balls at home, etc. I too was just doing what I could and I was so fat and out of shape it was very hard to exercise. Now I have been adding in water aerobics. But my point is don't become discouraged over what you can't do... you are obviously very busy... just do that walking!!
Congratulations on your desire to succeed!