I'm not sure I can be much help bexsybooboo I think you have to be mentally ready to lose weight. Something has to change in your mindset to be able to do it. I lost weight at 23 when I was 18 1/2st and got to 13st where I was happy so just carried on eating as I was. I have been unhappy with my weight most of my life but not enough to do something about it, things changed for me in November and I'm not really sure why but am glad that I have maintained my momentum as I don't think it's easy to it get back.
I think perhaps you should think about why you're losing weight, why you are eating too much (is it because of the stress from your job, because you're hungry, bored etc), tell someone (us, friends etc) when you plan to exercise to get you to go or go with a friend and perhaps vary it to keep you interested. Make sure no matter what a day throws at you you make that 30 mins to do something active.
3 stone is a massive achievement and perhaps that's the problem that you see those 3 stone and see it as another 3 stone/7 months of doing this and you can't see it happening. Perhaps have a week where you don't think about weightloss at all and if you put on a bit so what? Are there things you could cut out/decrease to allow you treats so you don't feel you're so deprived? I personally would rather have small portions so I can have snacks and found that a few weeks after cutting those portion sizes I wasn't hungry anymore. Perhaps you could go out and treat yourself to something in your new size to remind you why you're doing this and to help you feel better about it all?
On a practical note don't have snacky things/junk in the house if at all possible, plan meals before you shop so that you know what you're doing and don't get to the point where you don't know what to have an end up binging on what you find. Try to find something that you like, that's low calorie but fills you up, I love cherry tomatoes for this. Hot chocolate is good for sugar hit that fills you up and isn't too many calories. I have found that they less junk you eat the less you want to eat, you just have to get over those initial cravings.
Sorry to ramble just typed things as they came into my head, really hope you get back on track as 3st is a great achievement and it would be a shame to go backwards. At least you are maintaining rather than gaining though, I know it's not the greatest comfort at the moment!