Like the others, I agree you don't appear to be eating enough. That level of starvation will trigger low mood alone, without anything else.
It's a shame you don't favour yoghurt, as it's a great go-to standby for those hungry, or can't be bothered to prepare anything moments. We all have those. What don't you like about yoghurt? Is it just plain yoghurt or something else?
Can you eat nuts? I introduced a few nuts with my lunch, in an attempt to balance my calories versus energy, and that has helped. In an ideal world, I wouldn't bother with nuts, as I have to be quite careful. Too many (for me, means not very many at all), and there are unfortunate consequences, but to be honest, they are easy to consume, and I don't feel too tempted to over indulge.
The food diary is great. Using myfitnesspal, I was also able to identify I needed to eat more, and have continued with it since. Once you get it going, it takes moments to update.
Perhaps if you tell us what you were eating before diagnosis we could suggest some alternatives.
Starvation isn't the way forward to a healthy, happy and rewarding life. But, you know that already..