The first thing is not to panic!
I think for your age and the amount of activity you do, 1400 is too low. I'd deliberately raise it to between 1500-1600 by adding some good snacks--something with protein--like some part-skim ricotta with fresh fruit, or a South Beach Living high protein bar in the afternoon, or a serving of raisins as a snack with a string cheese--things like that. Or, you could increase the ounces of foods you eat--like have 4 ounces of chicken instead of 3.
Try that for at least two weeks, and if you keep your calorie average close to that amount, without any really high days, then you can see whether it's working.
Jay