I concur that I think you are not eating enuff each day. I read the same thing as BB ... if you multiply your current weight of 231 x 10 = 2310 cals just to maintain your weight. If you substract 500 (enuff to lose 1-2 lbs each week), then you should be eating about 1800 cals a day right now. Later on, you could lower it by 50-100 a day if you hit a stall or plateau.
If you are only eating 1200 cals and burning 400 cals exercising; you are in a huge deficit. 1200 - 400 = 800 in and 2710 out. Add the fact that you are taking meds too, and I'm not surprised to see these huge dips.
Yes, you need to talk to your doctor about this for sure ...