I have major depression and anxiety myself. I have found lately that when I get stressed I have the mood swings you are talking about. You are right, these short term highs and lows are not bipolar. I think it is your brain trying to level out, but can't find a "sweet spot". I recently started on Cymbalta and it seems to be helping a lot.

Are you on meds? Have you been diagnosed by a doctor? If not, maybe you should check into starting treatment. Therapy might help you too. There is a lot going on in our brains that we don't consciously think about and talking might help identify issues you are not aware of.

PM me if you want.