Hi Jayney,
You're down 31 lbs. and that is great! I love that fact that you are so eager to bump up your activity level! Having the right attitude and focus is most times what dictates whether a person is successful in attaining their fitness goals. You are on the right path. It sounds like you have been creative in your quest to burn calories. Marching in place when you can't walk around the building and using a stability ball instead of your normal chair are both great ideas. These are the things that will lead to your success.
Losing 1 lb. a week means that you are making progress each week. Keep up the good work.
Keep in mind that it is so important to continue to make your exercise program more challenging as it gets easier. If you haven't incorporated strength training yet, you should. The site has some great exercises that it recommends that you can start with.
Keep up the great work and keep me posted.
Good Luck,
Paul