Don't be discouraged. If you're not doing an intensive program, your progress will be slow--but slow isn't always bad. Slow is still real.

On the soda--I'd see if you cant find some kind of iced tea you like. There's more out there than the garden variety liptons.

Paradise iced tea is naturally slightly sweet w/o any sweeteners

Tejava is slightly tangy and astringent and is like crack to me

Diet Arizona Green tea w/Ginseng (uses splenda -- I go for the regular stuff myself but I haven't noticed much of a taste difference so they did a good job w/the formulation)

I'm not sure what kind of food you cook at home (or is Taiwan an indefinite stay?), but olive oil > butter. As much as I love the Julia Child "throw a stick of butter in the pan" approach, it's not exactly the road to wellness. To that end, I'll shill for a couple of my favorite cookbooks, by Kleinman & LaPlace, as I think variety is helpful when trying to stay within a diet. These are not diet cookbooks, but the cuisine is (mostly) naturally healthy (avoiding the obvious exceptions) or can be adapted.

Cucina Rustica: Simple, Irresistible Recipes in the Rustic Italian Style

Cucina Fresca: Italian Food, Simply Prepared (fast meals)

VERDURA: Vegetables Italian Style

I'm leaving out the pasta book, as I assume massive carbo loads are not the order of the day.

Good luck! Just keep going, you'll get there eventually. (That applies to both weight loss and riding roadsters, btw.)