Is it normal to not be able to distinguish dreams from real life?

I've been having very intense nightmares. Only recently however, I have found that they have been affecting my everyday life. For example in these nightmares there is a monster, about 100 feet tall, standing outside my window. You can only see the legs, but it's still frightening and incredibly, incredibly vivid. It's stupid really, I'm dreaming about big scary monsters again, haha. I'll often wake up in the middle of the night and look out of my window to see if it's there. It's really weird, but I'm on edge 24/7 and I can't stop thinking that one day I'll look outside an it'll be there. My boyfriend is comforting me about it, but unfortunately it doesn't do very much to help. Any thoughts?