I agree with keeping a food diary - that will help you see where your calories are coming from and what areas you might need to increase of decrease.
Make sure you get plenty of produce, both fruits and veggies; lean protein, low/no fat dairy, whole grains and "good" fats. Sometimes, we cut our calories TOO much and our body goes into starvation mode in order to hang onto fat reserves, so make sure you are eating enough calories. Make sure you opt for brown rice over white, whole grain pasta over regular, etc. Also, be aware that some fruits have a lot of sugar, which if not burned off right away, turns quickly to fat; and do eat whole fruit, rather than fruit juices in order to get the extra fiber.
Additionally, while running is excellent exercise, you may need to add some other forms of exercise to your routine, as well. If you do the exact same thing every day, your body becomes used to it and it's no longer a challenge. You might try running 4 days/week and do yoga, weights, or something else the other 3 days.
Although running is helpful and will keep you fit and healthy, cutting back on calories is actually more efficacious in terms of losing weight..
You've made a great start by cutting back some of the junk & you are doing great on the exercise. You are probably building up muscle from the running. Muscle weighs a lot & will make it seem like you are not getting better. Make sure you are drinking plenty of water. Dehydration will slow your metabolism down & tigerlilly is right: you don't want to lose the weight fast & seriously give some though about her food diary idea.
Sound like your doing a lot of things right.
Have you thought of keeping a food journal, if even for a couple of weeks, to make sure your getting enough calories and the right kinds of foods? You could also measure yourself to see if your losing inches instead of weight.
Don't forget even if you know what your doing your body sometimes takes a little longer to figure it out. Don't stop what your doing. Even if your not losing weight at the rate you think you should your still giving your heart a good workout and you need that no matter what.
I don't think you should lose more than 2 pounds per week, so if you want to lose 3 stone it should take you no less than 21 weeks. The slower the better. It gives you time for all the changes you make to become habit and they say the slower you lose the greater the chance of it staying off for good.