Flashbacks are like reliving events that actually happened....but it is also possible for your mind to kinda play tricks on you and you. I've developed that issue as well, sometimes there's all kinds of terrible stuff I can't get out of my head even though it has nothing to do with real events or what is going on in the moment.

Sometimes it feels the same as a memory though so it can be rather confusing, also I have a hard time getting enough sleep so when I've one a week or longer with very little actual sleep then I start confusing weird disturbing dreams I have for real events and that's when I really feel like I could go insane.

Also you may already know this but being under stress can certainly make symptoms worse and amplify the worst of them...so I guess I would recommend trying to reduce your stress that is what I have to do sometimes. I don't nessisarily like it because then I feel like such a loser because rather than go hang out with people or do something interesting I have to relax and make sure to keep my stress level down...or go somewhere quiet when I am 23 and people seem to expect that i should be striving for some great oppurtunity or this or that or at least having fun and experiancing all there is in life or whatever, not having to be careful of my stress level and constantly monitor if I am ok to be around people or if I should maybe have some time to myself and such.