I kind of understand what you are talking about.
I personally experience a sort of… incomplete memory, you might call it, of rages. In the worst ones anyway. It may be just as well. I'm mortified over them as it is. Really strong emotions can bring on a disconnect, and rages definitely are that(!)

The most extensive (and downright disturbing) overload memory loss for me was a night I woke up in the extreme pain of my life (which is a long time). I'll spare details, but it was the only time in my life that I actually asked (cried out begging, more like) to be taken to the ER. I had no memory of 90% of what happened(!!!) Days later BF filled me in (on most of, as you will see). I was incredulous. These were things that should have been very memorable(!) At a followup appt., the doctor said, "let's look at the x-rays". My jaw dropped, "There were x-rays???!!!!!" She looked at me like I had 7 heads. It's 2 years later now. The "filled" in (by BF) parts are still extremely blurry, more like a dream you can't quite remember than reality. I still have zero memory of the x-ray. But I saw the film, so it must have happened(!)

Anyhow, it's interesting that you say you go "out" for 3-4 days. My BF does this sometimes too. He is not his normal self (and can be scary sometimes in the midst of). I have always felt immense relief when he comes out of it, and have always referred to it as "having him back". He does experience emotions very strongly. (None of his dx's really account for it, so can't help you there.)

On the epilepsy check…. it's something I've heard before, and even upon reading up (just now), I don't totally understand it either. But. There can be a loss of memory component. Also, some of the meds used are the same as used for BP. So…. again, not sure exactly, but seems worthwhile. Might be in order to rule that out, as other have mentioned above regarding symptom causes.

Good luck. That sort of loss of memory can be very disconcerting.