I'm truly sorry that you're struggling so much.

I'm curious as to why you see these issues as 'mixed' episodes? From what you describe, they sound like very rapid changes in mood that last for very short periods of time. They could be relatively 'normal' ups and down (as you say they, for the most part, don't impinge on your life too much) or they could be ultra rapid cycling (which is controversial in parts of the psychiatric field as part of a diagnosis) or it could be intense reactions to life events that could either indicate BPD or otherwise being very sensitive to what is going on around you.

Do you have a therapist? I think getting a hold, first and foremost, on what is going on with you, will help you find a solution. A mood stabilizer might help, but if, as you say, it doesn't impact you too much, maybe therapy would do the trick. Best of luck in feeling better!