I'd accept that it's not a usual experience, and having experienced something similar to it in my youth, I understand it is very scary. That said their are many traditions where such a dissassociative state might be considered spiritual. I'm not going to go all hocus pocus on you, but it might be interesting to attempt something creative during the periods (if you're not in the middle of town on a Saturday. Some abstract art created in this state would be very interesting from an artists perspective (Apo will no doubt have something to say, he's an adept artist!!), but also if you were to eventually see a therapist some sort of art diary would be very interesting and helpful for them. If you're not into painting or drawing perhaps keep a journal/diary and do some free association writing??? Has to be worth a try beyond self harm???