Worried about low calories, what can I do? Long.. please help?!!!?

I've gotten to the end of today and I've only eaten 900 calories which I know is bad. I'm already seeing a counsellor about depression issues and eating problems, as I've lost a lot of weight and only eat around a 1000 calories a day so I am trying to increase the calories without putting on weight as I still have belly fat I want rid of. Here's what Ive eaten today:

BREAKFAST: 100g low fat greek style yoghurt with blueberries and a sprinkle of muesli, with a slice of wholegrain toast and weight watchers marmalade. (217 cal)

LUNCH: one egg plus two egg whites omelette, with chopped slice of ham, mushrooms and spring onion, with romaine lettuce, cucumber, and reduced salt ketchup. (184 cal)

SNACK: an apple and a few pinches of granola from the bag. (110)

DINNER: thin cut grilled peppered steak, half a small jacket potato, brussel sprouts and broccoli. (345 cal)

Throughout the day/at meals I had 5 glasses of water and 4 cups of decaf tea.

Total calories is 893, even though I reckon I've eaten healthy normal sized meals? I'm stuffed after dinner now but don't want the calorie intake to be so low :( Shall I wait an hour and have a yoghurt with raspberries or something? I also did a paperound (so walking) for 45 minutes.