Believing I'm being kept in a hospital in everyday life

I don't know if this is the right place to put this but I am struggling a lot at the moment and don't know where to go for advice.
Basically I go into this state (usually at night but a couple of days ago I had it during the day and walked out of school) where something inside my head is telling me I'm being kept against my will in a hospital. It's like I'm two different people inside and it's someone else thinking. I'm not sure if that makes sense. But it's not just believing I'm in a hospital I also see it, it's like with my eyes and outside my body I can see that I'm in my bedroom or I'm in the street or school but once it's in my head I see those things as the white walls of hospital corridors. The other day when I got bad and walked out of school was horrible because I didn't understand what was going on - beside me as I walked were hedges and stuff and I could see that, I could see it was green but still my brain told me it was white and smooth and I reached out to run my hand along it as I walked and it scraped me and I was just so confused and out of it. As I said, it's like someone else is thinking inside my head and once I come round again I know it wasn't real but it still feel horrible that I don't have control.
Anyone else experience anything similar?

This sounds like schizophrenia. You need to see a doctor or therapist as soon as possible. This will only get worse. Please seek help.