The general consensus is not to use tense forms which have "be" or "been" + "being" because it sounds clumsy. Native speakers don't really use these forms, though perhaps "will be being" is just about possible. In your example, with the main verb "to be", there is no discernible difference in meaning between "I have been" and "I have been being". So the short answer is: don't use a continuous form - there's no need.