Why can't I eat more?

Well that might seem like an obvious question, but what I really mean, is why am I struggling to consume more than about 700 calories a day? I was advised to aim for about 1000, with 1200 as a top limit - and I'm not even getting close to the lower limit. Take today for instance. It's 9.30pm in the evening and I genuinely am feeling quite full. I had a very filling low fat creamed rice for breakfast, a cottage pie for lunch and a three part evening meal (salmon, butternut squash and cauliflower) - the first time I've managed a three-part meal since pre-op times. I don't really see how I could have eaten more than this without increasing the volume of each meal. I am not supposed to do this because it can stretch the newly created stomach pouch.

I am genuinely confused about this. I need to speak to my dietician about portion size and calories etc. When I have some more light to shed on this I'll post an update.