Calorie counting. That's the only thing that works for me...even if I count after a day's worth of eating and I've gone over...at least I KNOW. It takes a whole 5 minutes and keeps me accountable.
Have you been weighing yourself? Even if you're maintaining, it'll be pretty tough to control your weight without tracking your food or weighing.
Then again...you could always use your clothing as a gauge.
Don't kill yourself if you've gained, you deserve to enjoy this new experience and the holidays, and most of all YOUR FAMILY!!!
You've noticed that you may be gaining, acknowledged that you don't want to gain more and that you need some kind of routine or prevention plan to keep the weight off. That's a huge starting point! Just pay attention to what you're eating, and try to move as much as possible if you can't calorie count or weigh yourself.
Good luck, and congrats on your weight loss, I know you can maintain it!!