It might be because you use to much yeast. You can experiment on how much yeast you actually need in your bread. Start by using half. If it's too little, use the amount you used + 50%. Repeat until you have found the perfect amount of yeast. If it's too much yeast, you should no longer taste it.
EDIT: Could also be because you let it raise to long.
You can't bake bread to end up without crust, as it will always require high temperatures that will toast the outside (to varying degrees) without just dessicating the entire lump of dough.
For pure crustless bread, I would try to make something like a giant steamed dumpling. There are a few examples (courtesy Jefromi and Jay's comments, respectively) of this in Chinese cooking: baozi, a filled dumpling using yeast dough; or the larger mantou, similar but without filling.
When steaming dough it will retain much more (nearly all) water, so a drier dough would be in order. Generally in most bread-baking, the goal as Julio mentions is to get the inside to 200-210 °F, and by using steam at ~212 °F, you will get virtually no browning.
That said, crust can vary wildly, from very soft to very hard. The softer crust breads I bake are usually done in pans at lower temperatures (325-375 °F) and often contain milk, eggs and or fat. The more "crusty" breads are usually baked quickly at hot temperatures (>450 °F), but if done lower and slower it will change the crust significantly.
Best Answer
You could look into making flatbread, which often (though not always) gets its name through being unleavened, and thus, flat (yes, I am oversimplifying here). Common examples are tortillas or roti.