Hi, first congratulations on losing 20lbs!!
Next time you go in a grocery store, pick up a 20lb bag of potatoes-That's a LOT of weight!!
I like to walk outside too and am really looking forward to Spring!! Not being able to do the things I like most is tough, but I know I have to do something besides sit on the couch when it's cold/wet outside. So, I have lots of workout dvd's, some I like, some I don't care for, but I make myself do one if I can't get outside. Maybe you could try one of them-one of my first workouts after finding SP was the Walk Away The Pounds ones-I still do one sometimes, except now I crank up the stereo or MP3 player, mute the sound on the TV (since I've pretty much memorized it & the same chatter gets pretty annoying afterawhile), and just walk!!
The music gets things pumped up so I don't get lazy :)
And other days I do my strength training-I try to mix things up as much as possible.
Don't worry about going backwards-you are doing great and as long as you use the trackers and STAY CONNECTED here no matter what, you will be just fine!!