I don't think you are baking your bread long enough, and probably not at a high enough temperature. Most bread recipes I use bake anywhere from 45-50 minutes up to 65-70 minutes.
I would try raising the temperature up to at least 375-400 and give it at least 45 minutes. You might need to cover the bread loosely with tinfoil after a while.
You can try knocking on the bottom of the loaf and it should sound hollow.