If you're really serious about losing weight, you need to get serious about your eating. Start by keeping a detailed food journal for one week, without changing any of your eating habits. Be as specific as possible, measuring when you can, looking up your calorie and nutrient content and adding up your calories for each day. You'll be surprised how those calories can sneak in when you're not keeping track. These resources can help you get started:
10 Ways to Control Portions
Keep a Food Diary
FitWatch Fitness Tracker
Something else to think about is metabolism, which can drop as you get older if you don't preserve your muscle mass. Some estimates show that muscle mass declines about 4% each decade from age 25 to 50. If you're still eating the same number of calories as your metabolism drops, your weight may creep up over time. Start exercising and lifting weights now to keep your metabolism in check.