I don't think mood swings during the course of a day is intrinsic to BP; to some extent (if not extreme) it could be 'normal' and better not to overthink it.

On the other hand, in your case it seems to be causing a good deal of distress and I would discuss it with your pdoc. It may not require more or a change in medication, but maybe your pdoc (and/or T if you have one) can help you clarify what is happening -it sounds very frustrating.