Am I having drug flash backs or is my brain malfunctioning?

So this is what keeps happening. It started yesterday, and I’d say it has happened about 3 times since then.

I am doing some simple simple task, like throwing away trash or getting something to drink and all of a sudden I’ll have a vivid memory of a dream, though I am not really sure it’s a dream, it could be a memory of an actual occurence, but it will completely become my reality for about 3 seconds. During these 3 seconds or so my heart kind of races, and I get very jittery (very similar to the feeling one get’s when the LSD starts kicking in). I take a few deep breaths, focus my attention on something concrete, it fades away, and I cannot remember the memory/dream at all. I try, but it seems to just go back from whence it came—from seemingly nowhere.

Is this a flashback? If so, why am I having more than 1 in a small period of time? If it’s not a flashback, what else could it be. Have I finally broken my brain?