I don't understand - but I like it

What is happening to me? When we were away on holiday last week I was eating quite large food portions. I didn't gain any weight because we burned loads of calories walking. As soon as we returned I resolved to get back to smaller portions and healthy eating. This past week something very odd has been happening. I've been gradually eating less and less and getting less and less hungry. This has come to a bit of a head today. Here's what I've eaten (calories in brackets):

Breakfast: Two small pieces of bread topped with warm tuna and melted cheese. Also orange juice and an Actimel drink. (300)

Lunch: Mixed salad vegetables with adzuki beans and a scoop of cottage cheese. (125)

Evening meal: Salmon, rice and frozen mixed veg. (230)

Other: Ben and Jerry's ice cream tub (at cinema). (230)

Now, dinner was actually 460 calories but because we went to the cinema quite early, I decided to split dinner in half. I ate half before we went with the intention of eating the rest when we got back. While at the cinema I had a B and J ice cream. Anyway, when I got back, I got the rest of my dinner out of the fridge and smelt it - mmmm, lovely! I picked at a couple of bits and ate them - a tiny piece of salmon and a bit of green bean. I knew immediately that there was no way I was going to be able to eat it all. I felt absolutely stuffed! An hour on, I'm still feeling stuffed to the point of nausea....?! My total calorie count for the day will only be about 900 - it hasn't been that low for months!

I reported a similar experience to this on August 10th. All this last week I have been experimenting with splitting either my lunch or dinner in two - thus having four meals per day. I've also been eating whenever I've been hungry - healthy snacks like fruit or yoghurt. And at the same time I seem to be experiencing real restriction for the first time. I am seriously considering cancelling (or at very least, postponing) the fill I have booked on August 23rd.

As ever, I'll keep you posted - but I am feeling quite optimistic about my restriction at last.