Hi
I use to feel like that, 'not in my own body' and when I eat certain foods, it returns. It turns out I have a wheat allergy and if I have too much, the out of body experience occurs. It is also brought on by excessive dairy products milk etc and caffine heightens it. So it may be that something in your diet, doesn't agree with you. Try and eat non processed foods for a few days and see what happens, maybe cut out wheat products too. You never know. As they say 'you are what you eat'.
Hope that helps