One other thought to add to all the others ...
If you've lost 75 pounds and your only exercise has been walking, chances are that you've lost a fair amount of muscle along the way. Studies show that up to 40% of the weight you lose by dieting will be muscle, not fat, if you're not lifting weights or strength-training (same thing) to maintain or build muscle while you're losing.
Unfortunately, walking isn't muscle-building exercise. Jill's right - those ten pounds you've gained aren't muscle. Walking is awesome cardio exercise, burns calories, and you should definitely keep it up, but it's not going to do anything to preseve or add to your muscle mass. For that you need to be lifting weights.
The effect of losing muscle as you lose weight is that it lowers your metabolism. Muscle is metabolically active tissue that burns 20 - 25 calories per pound every day. So if you lose ten pounds of precious muscle, for example, your metabolism will drop by 200 - 250 calories per day and the result is a slower weight loss or even a gain.
Have you ever had your body composition (body fat percentage) checked to determine the % of fat and lean body mass that you used to have and have now? That's the best way to determine whether you're losing pounds of fat or pounds of muscle. Our goal shouldn't be just to lose scale weight - it should be to lose pounds of FAT!
You might want to consider adding some weightlifting to your walking regime. Building back some muscle will speed up your metabolism and let you eat more and still lose weight. Good stuff!