Stuck in a rut (Help!)

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I have been using MFP since about mid Jan 13 and have been sticking to approx 1200 cals a day, obviously with one or two days being slightly higher or lower. I have lost 16lbs which means I am now 12st 8lbs. I have been this weight for about 2 weeks now and not sure why as the weight was coming off fairly quick. Now its just stopped altogether. I havent been bad food wise and have been trying to do bits of exercise. Any help or comments of own experiences would be helpful.

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