I don't know what it is but I've felt EXACTLY the same. I was in a car park one evening and had the same deep scary thoughts as you, what's life,what are we doing, who are we, what's the point etc etc. I also started thinking about people a lot stupid observations leading me to think really cynically about everything. Like the fact that no one cares about anyone, people are only kind to make themselves feel better, everyone is selfish and can we ever be happy? Aren't we always waiting for it to get better or getting nostalgic and wanting to go back in time. They got worse at weekends or on long car journeys when my mind was left to wander. I felt like I was floating away from my body and from the world. It has improved since going back to school after the holidays but I still have dp because I just don't feel connected to people or my memories anymore. Similar to you I have exams soon and can't concentrate during revision. My advice therefore is keep busy and talk to people even if it feels odd and horrible. Get involved in the world around you as much as possible. Listen to music and sing the words in your head if the thoughts get really strong. Exercise and concentrate on the pain of it (running is painful I'm so unfit lol). Try to get lots of sleep. Do you know why you got this? Did it just suddenly come then or build up at all?