How did you set your 1,200 calorie diet? Frankly, I doubt you are eating enough. That amount is the *minimum* for the average sedentary woman to eat to support basic bodily functions. If you are exercising as well, your body thinks it is in crisis and has slowed down your metabolism. It is biologically programmed to save you from famine. It has no idea you are doing this on purpose.
I encourage you to use the tools on this site to set your calorie range and match it with your exercise routine.
BTW, the scale lies and only indicates weight. Being healthy and fit should be the goal. There is no magic number.
And, you must accept the fact that your body just created an incredible human being. It may not ever go back to the same size and shape. That's not to say you don't want to eat healthy and exercise. Just be open that it may be different, but just as beautiful and strong.