Having difficulties due to past habits

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I used to be anorexic. When I had my first child I decided to start actually eating and show her good eating habits well all that happened was weight gain. I know its from a slowed down metabolism and blah blah blah. I'm trying to regain all that back and lose weight to. I'm on my feet all day cleaning, chasing my girls around, cooking, working, playing outside, yada yada, yada. I eat between 1200-1700 calories a day and no change at all has happened all month. Anyone have any ideas on what I can do to speed up my metabolism? I also work out either while my kids nap or after i put them down for the night.