Is it normal to have some problems discerning reality?

Sometimes I second guess myself as to whether something is real, usually when interacting with other people. I'll frequently trail off in the middle of a sentence to check whether I'm really talking or maybe it's just that my mouth is moving or maybe I'm not really talking at all.
Other times I'll think someone's mouth is moving (as if they're talking) when it's not, or that a sentence or a laugh is in my head when it comes from a real person. Sometimes pieces of time will disappear and I won't be sure how one sequence gave way to another. It's annoying, because it takes me a while to react to anything- did this guy really spill soda on my shoes, or will it all go away when I blink? I feel really disconnected to everything, and it makes me feel lonely.