I see that the starter of this thread has deleted their account but for information of those that may be seeking this...

the difference between regression and DID is that regression does not have alternate personalities taking control.

anyone mental disordered or not can regress (feel like a child, talk like a child, have emotional reactions like they did in childhood.)

here in my own location another term for regression is the child with in therapy approach. a common example my ow treatment providers use is think about a time in your life when you felt as happy as you did when you were celebrating a favorite holiday as a child, now take that moment and think about your present life and you will be able to find where in your present life you have felt the same thing, talked in that same happy/excited tone of voice. now think about a sad time in your childhood and a present sad time you will notice similarities of how you talked, felt and reacted.

for some people these normal regressions of feelings, tone of voice and reactions can be scary if they have never noticed human beings naturally go through these natural regressions. especially if its something that is a really emotionally charged situation where these normal regressions seem to be extreme.

(which brings me to another difference ...with DID a person has been DID since very early childhood so their switching into alters is neither scary or frightening which ever word you use. its just their normal way of being.)