Thanks very much, peeps! After a day and a half of this, I can honestly say I'm feeling more optimistic. I'm tracking all of my food, walked the dog 3 miles this morning, and I even cooked a healthy (and yummy) dinner last night.
I think my apprehension comes from always just being able to eat whatever I want and not gaining weight... that's obviously not the case anymore. I'm just not used to having to pay attention to what or how much I'm eating. I don't feel worried at all about gaining more weight, I just am not content with where I am right now.
Thanks so much for the suggestion about 5k's! We've actually been talking about 10k's and half marathons.
I have never been a runner so a 5k seems much more do-able.
I value your support - hopefully in a couple of months I'll be writing about how I did it!