I have it too, my personal belief is that energy center solar plexus under ribs area, reaches out to future places your going to go, people your going to meet. It's the ego/protective center so it checking out things and bring back info. Most of us aren't raised to understand it so it can get confusing and disorienting. Basically I think it's the body telling you, yea I already told you we'd be here or meet this person etc.

Of course - disclaimer - we have bp and supposed to watch out for psychosis. Some things are early signs of psychosis. But most of déjà vu I consider so normal for a sensitive person.

I also have the dreams. Often it's a situation I find myself in at some later date, and know to make a different decision choose my path for a better outcome than what was often a tragic ending in the original dream.

This is just my experience, personal beliefs.