Hi wannalose8stone
Well, last things first - I'm around 12 stone 10 (BMI 27ish) and I eat around 2000-2500 calories per day to maintain, or 1700-2000 if I am trying to lose weight. I'd like to eventually end up somewhere around 11 stone but I'm in no hurry (I'm currently working on muscle gain, which sorta precludes any kind of weight loss for the time being

)
Right, enough about me, let's talk about you. I can't really say whether you need more calories (although from the sound of it, quite probably!) without knowing more about your exercise routine. Did the trainer who put your programme together know how many calories you were on and take that into account? How long is your session? What kind of balance of cardio/resistance? What intensity? Are you aiming to progress i.e. increase your weights every couple of sessions, increase your speed/intensity on the cardio machines? What is the goal of your programme?
Well done with your loss, by the way - that's fab! I bet you feel fantastic.