Spartan girl, what ever you do, don't go back to the one meal a day. That will destroy your metabolism and make it even harder for you to lose weight, OR maintain it when you get there. Your body will hold onto all of those calories because it is afraid of starving with so long between meals. Stick with the 1200-1400 calories a day like your doctor suggested.
Are you tracking your calories, every single bite? Try getting an account at
www.fitday.com . You might be eating more than you think. I was just reading today that the reason most diets don't work is because people underestimate how much they eat and overestimate how much activity they get.
Have you tried alternate food combinations? Some people do better with low fat, some with low carb and some low glycemic. Look around our message board, there are a lot of options available to you.
How much do you exercise? Have you tried lifting weights? More muscle takes more calories to sustain. You can burn more calories per day by having more muscle weight.
Hope these helped. Above all, if you are gaining weight and you know you are eating the right calories and exercising, please go see your doctor.
PS- If you want to post here what you eat, maybe we can offer suggestions.