Why does frozen bread sort of taste different?
Over the short term moisture is "locked into the packet". As bread freezes moisture from the bread often condenses and freezes on the inside of the packaging. If you then defrost the bread slowly in the same packaging this moisture is reabsorbed. If you only defrost a few slices at a time this moisture is lost when you take those slices out of the bag. These ice particles can also end up in your freezer rather in the bag. 

To keep the moisture level closer to the original: freeze bread in portions you are likely to defrost them in and make sure any bags or wrap you use is suitable for the freezer. If you freeze whole loaves double bagging them or wrapping in some way helps.

These steps will also stop other flavours from your freezer being absorbed which should help.