Camera iPhone keep on when I’m asleep

I have seen my usage time quite often to see how much time I have use for each of my apps. Recently, my usage time have gone up 40% and it shows even when I’m asleep my camera is on. I don’t know what is the problem, I have always closed my apps when I’m asleep. And it is usually not like this. The battery and everything else also showed most recent apps that I use