starting again

Hello,
I started on this site awhile ago, did a great go of it. Changed everythiing i was doing wrong, went from 140 to 110, to 115, to 112,
Now After some time passed, I have gone back to some of my old habbits, and am now back to 126 and very un happy,

I am lookinig to get back the results I had when I first started,I am a P.S.W so im on my feet often with work, mostly running around from room to room, getting this or that and taking clients here or there and doing what they need done for them but it doesnt seem to affect mym weight at all, I am not losing any weight by my job.

I have 8 flights of stairs in my building, and miles of sidewalk to jog on,
I have an excercise bike as well, but it didnt seem to do a thing for me either,

I was hoping to get some help in where to start for jogging, I have no experience in jogging,And would like to start doing this as I have heard it is great for weight loss, also , is there anything I could do with a routine for the stairs I have in my building?
any help or suggestions would be greatly appreciated,

Thank you in Advance