Try cutting calories, but not by a lot. I know it may be hard to change your diet, but you wont lose body fat with out it. Even try only drinking water. There is NO WAY of only targeting one area. If you want to lose the tummy, you have to lower your body fat, and you can not lower your body fat with spot reduction.
What I suggest with you is a lot more cardio. Try going on a jog for 30-45 min every day on top of your daily walking. Also you do not need a gym to exercise. Here is some exercises you can do. http://sportsmedicine.about.com/od/t...ictraining.htm
I suggest doing 4-5 exercises for 12 sets and 4 reps after cardio. Always try to switch up the exercises you do.