I think maybe you need to eat more, especially for breakfast. If you don't eat enough breakfast, your body decides it's got to make do with very little that day, and does it's best not to burn anything. Try some high fibre breakfast cereal with the fruit, like bran or muesli or weetbix (find one you like the taste of).
And yeah, watch portion size. I've eaten very healthy foods most of my life. But healthy foods in large amounts are just as bad as unhealthy foods.
What's in the soups and stirfrys you're eating? Sometimes it can look good, but if you check the kilojoule content you might be surprised. Cream of soups aren't so good, or fatty stirfrys.
Finally, and I hesitate to bring this up, but if you're very tall you might already be at your ideal weight. I can't tell either way, but it's possible that you aren't loosing weight because you don't need to. Unlikely though, else why would you be here?
Don't give up though. Even if you don't see a change, the lifestyle changes will really help your health, especially all that walking!