Hi Payling,
If you're using the flour that the recipe specifies it's probably not the flour. If the recipe is specifying cake flour and you're using all-purpose, it would definitely make a difference.
There are many things that could make your cakes soggy.
Make sure your baking powder is newer than 6 months old.
Use a second baking thermometer in your oven to make sure it's reaching the proper temperature.
Perhaps the recipes you're following are a little off? You could try different ones or try reducing the water and/or oil content a little.
If you're adding things like fruit to the batter it can release juices during baking that can make cakes soggy. I usually reduce my water and oil content a little when I bake these types of cakes.
Good luck and let us know when it works out!
