I think what you are experiencing is the ''deja vu'' effect. I had this problem for some months, where every couple of minutes I felt a strange sense of familiarity as if I had just lived that moment. Maybe I was on vacation in a place I had never been before and it felt like I had already visited that place, almost as if I had lived what I was experiencing in an earlier life.
It was overall very confusing and made it hard to focus on things, as this feeling was brought constantly. It may be normal to have a deja vu once in a while, maybe once a year, but it usually lasts a mere second and you are instantly back to normal. I had it very frequently and intensely, but after some months the episodes slowly stoped coming and I could live normally again.
I've read this is related to the memory area of the brain, that instead of the brain processing the experience and then storing it as a memory, it does the opposite, it stores it first and then processes it. So when it's processing it, the brain finds that the memory of the experience is already there so it sends a signal to inform the experience is a familiar one, in fact so familiar it is the exact same one.
There are scientific studies about deja vus and you can easily find them on the internet to know more about this. I remember reading in one of the studies that some epileptic people experienced a deja vu like sensation right before their seizures.
I have to admit I had a couple of months of cannabis use before this incident and the symptoms went away when I quit smoking. I had experienced mild and short deja vus as a kid, when I didn't smoke yet, but not of such a severe magnitude. There are people that never experience this in their entire lifes, but it is not rare at all to have mild sporadic episodes once in a while. So the episodes from my childhood were normal, but the long ones I had as an adult after smoking weed were not, so weed might be the cause. This has also happened to a friend of mine that used to smoke a lot.