How can I get my bread to be more fluffy and less dense?
A big factor besides the dough is the temperature at which you bake the bread.

If you are not baking it at some recipe specified temperature you are probably playing on the safe side and your breads won't raise much.

You have to heat the CO2 pockets quickly so that they expand before the dough hardens. The more temperature you can give it the better.

Another possible factor may be the yeast. Are you waiting enough? Are you using enough? Like temperature, more yeast and longer fermentation times can't go wrong.