help to fix diet/how to tell if I've burned fat not muscle?

Sorry not sure. Maybe a dietitian or personal trainer can help?

You're going to probably gain weight if you've been eating at an extreme calorie deficit (you have been), and then decide to eat the proper amount of calories. Hold on! It's not all bad news. You will lose the weight after your metabolism has got itself back on track.

You probably have lost some lean body mass, but you can gain it back by eating right and getting enough protein in your diet. If you're working out and eating at a calorie deficit, then you'll lose the fat, so don't worry so much about that.

Definitely start eating more STAT! And you might gain until your body adjusts and trusts that you're properly fueling it, but it'll come back off. Go get a set of dumb bells and do some workouts at home. Or even lifting gallons of milk works. Be creative. You don't need a gym membership to lift weights. Also, like previous posters mentioned, body weight exercises will help as well. But whatever you do, EAT.

Try to up your calorie intake gradually, like 100 or 200 calories more every one or two weeks. That may help to prevent gaining back most of what you've lost. You will by no boubt gain back some, but just like the others said, you'll probably lose it again once your metabolism has adjusted. The adjusting might take some time, depending on how long you've been eating at such a great deficit and how/what you've been eating before.

You should definetly try to build up muscle again. You don't need access to a gym for that. Check out pilates (I recommand blogilates.com, Cassie has some serious *kitten*-kicking workout as well as introducing beginner videos), yoga (maybe Tara Stiles?) and especially calisthenics ('You are your own gym" by Mark Lauren is awesome).You can do all this at home without having to buy expensive equipment. You could do this 3x a week for 20 or 30 min (at the beginning and later on do more) in addition to doing your cardio 3x a week. It would be good if you had at least one rest day and more beneficial if you wouldn't do strength and cardio on one day (maybe something like monday: pilates, tuesday:cardio, wednesday:yoga, thursday:cardio, friday: you are your own gym, saturday: cardio, sunday:rest?).

Hope I could help.Take what you need from my advice and adjust it to your needs and interests. You will fix this, don't worry. it just might take some time and effort.

Eating more is definitely healthier. Focus on trying to eat as much food that is not processed as possible. You might see a temporary weight gain when you increase your calories, but give yourself a month and it will start to drop again.

Based on your exercise and stats you can probably eat upwards of 2300 calories a day before gaining fat. Also based on your stats you should be closer to 1800 calories a day. Now the issue you will run into is you have probably suppressed your metabolism due to not eating right. I would definitely try to get up to 1600-1800 over the next few months to stabilize hormones and work on cutting fat... not weight. Weight training will be the most effective way of doing that so look into adding weight training or getting some resistance bands.

This is the best advice you've recieved so far. Additionally, based on how little you were eating, you can be sure that you lost some muscle mass. Following the advice above will prevent that from continueing.

Thanks.
I'm not bothered about being toned and muscular, the only thing that bothers me about losing muscle is that that means I'm losing less fat. I really want to lose fat and look more petite.

The thing that really frustrates me is that I haven't lost many inches, I've lost about 3 inches and 2 dress sizes. I was in a size 16, now I'm a size 12. I should be less than that if I've lost 2 and a half stone shouldn't I?

Well there is a strong chance that you lost up to 50% of your weight from muscle. But now that you know that, correct it. Start to add another 100 calories a week until you hit at least 1600 calories. Then you will have to sit there for a month and then probably up it to 1800. But adjust your macro's and work on heavy weight training. This is where you will see the greatest changes in your body. In fact, throw the scale away. When you up calories, you also up carbs which will increase the amount of glycogen/water stored. I generally see up to 5 lbs of extra weight. Increasing protein and fats can help eliminate some of the water weight if you are worried.

If you struggle to get calories there are a few things to do.. first eat nuts, add avocado to foods, cooking meat in evoo or go to town on a peanut butter jar. Step two, until you can up your calories, do not exercise. There is no reason to tear muscle down if you wont supply it with food to repair your muscles. Until you fuel your body, you wont stop catabolizing your lean body mass.

your metabolism only shuts down when your dead.

eating smaller frequent meals to keep your metabolism running is a myth that needs to die but somehow never does

Thank you.
I haven't exercised for the last 3 days and I skipped a day at the beginning of the week. I think what I'm going to do is not exercise for a few weeks, up my calories by 100 a week until I reach 1600 and then restart my diet in January or February. Does that sound good?

Sounds like a good plan. Also find a way to incorporate resistance/weight training. You can even ask for a few resistance bands for xmas, lol.