Wow, I'm surprised no one has mentioned this, or maybe they did and I just missed it.
One thing that you can do, and that I have done successfully is spread your food out over 5 or 6 "meals." Find a calorie calculator online as someone else suggested, figure out how many calories you burn and how many you consume. Spread out your optimal calories over 5 or 6 meals. For instance, eat a bowl of oatmeal and yogurt for breakfast. Then have a banana mid morning, then maybe a grilled chicken salad for lunch, then a protein bar mid afternoon and maybe a grilled chicken breast for dinner. That should run your around 2000 calories a day depending on portion. So say you burn 3000 calories a day, it will take you 3.5 days to lose a lb.
Another thing to consider, and maybe you already do this, but you can add weight lifting to your routine. Maybe do 3 days of running and two days of lifting. Building muslce mass is one of the best things you can do to lose weight because building muslce increases your metabolism which allows you to burn more calories even when you are not working out.
Another thing is you have to change up your regimine. Our bodies are able to adapt and get used to what were doing so you have to throw it off and do something else otherwise you wont realize the same games you were before.
Another thing you may want to try is interval training. Rather than just running at 6-7 mph hour for a half hour to an hour, incorporate some interval training. If you're not familiar with that, what you do is you go in "spurts." Get a good warm up in, say five minutes, then run at 7 mph for 2 minutes, then back down to 6 mph for 2 minutes, then back up to say 9 mph for 2 minutes, back down to 6 mph, then up to an all out sprint for 2 minutes, then back down. This is another thing that will help keep your body on it's toes. Also consider adding hills into your treadmill routine.
So, in conclusion, spread your food intake out over 5 or 6 "meals" and add weight lifting to your workout routine. I'd be willing to bet you will start to see results within a week or two.