My suggestion to you is find someone that can help you with your diet. You should keep a journal for a few weeks. Eat as you normally do then find someone to help you with your eating habits. How long do you exercise for? Have you ever read Body for Life? It is a very good book with eating and exercise suggestions. If you dont want to buy it I am sure it is at your local library. Good luck to you. Remember to drink alot of water and lay off sodas if you are drinking them.

Drinking more water is important, but I really doubt it's the cause of your woes. Diet is going to be a huge part of it, but you need to increase your workouts as well. If you're just at a walking speed at a small incline, you should really be aiming for a longer duration. 30 minutes at least, ideally closer to 45 for now. The longer you go, the more fat burning you'll get out of it.

Weight loss is mainly dictated by nutrition. Exercise sits in the back seat relative to your nutritional habits on the spectrum of importance.

You could exercise until you are blue in the face.... yet, if you are eating more calories (energy) than your body needs each given day, you are going to store it as fat. Simple as that. Thermodynamics at its finest.

That said, you really need to work on your nutrition. How do you eat now?

I have read that people who have a slow metabolism tend to lose weight at a slower rate. But it didn’t say much about how much time it will take for a person with slower metabolism to lose weight. I find that 6 months is too long. According to me the best thing you can do in this case is to visit a dietician. He will in a better position to help you out.