Hi Kat!! and
This site is just amazing, full of all kinds of information and tools to help us on our journeys to a healthy lifestyle. Best of all is the caring Community of fellow "Sparkers" ready to offer support and encouragement.
I think there are a lot of us who, like you, don't have the motivaitonal buddies in "real life". My DH is supportive but doesn't really understand how excited I got when my underwear was too big and I had to buy smaller ones (!!).
At any rate, there are plenty of people here on Spark who understand completely. What I would suggest, in looking for a buddy-- I see from your SparkPage that you've joined a few Teams. So be active on those Teams, post to the discussion threads, read other people's blogs and look at their SparkPages. See if there is someone who strikes you as a "kindred spirit"-- whose goals or life circumstances or motivational attitude, really strike a chord with you. Then, send that person a Private Message. This is like Spark e-mail. Strike up a conversation, see if that person is interested in being an "accountability buddy".
Don't be discouraged if someone else turns you down-- they may have issues going on in their own lives, where they don't have time or whatever. Keep looking and I can guarantee you'll find someone. At the same time, don't stop being active on your Teams. We're all only human, and it would be a shame to depend so totally on one other person to help you, that if she gave up, you'd be lost.
As for the physical activity-- I think it would be really important to check with your doctor(s) for what would be appropriate. Not only, what kinds of activities, but also how many minutes to start with, and a plan or schedule, on how to build that up. I was a complete couch potato, and started with only 10 minutes a day.
Keep in mind that what we eat plays a bigger part in weight loss; exercise is important, but we really need to be using that Nutrition Tracker. If you're not sure how to use it, this video explains that: www.sparkpeople.com/resource/nutrition_art
I wish you much success!!