Weird Dreams.

I keep having this weird dreams that are almost real, so real that when I wake up I get confused for a while thinking if what I dreamt I really did it or if it was just a dream.... There´s no problem with that.., the problem comes when you do bad things like in my dreams...., they stop being dreams and get converted into nightmares..... What´s the difference between a dream and reality ? Studies have shown that the same areas in the brain get activated whenever you´re seeing something or dreaming that something.., so another question here is: Which one is really seeing? The eyes or the brain ?? And again.., what´s the difference between reality and dreams ? The only answer that comes to my mind right now is that dreams are not as consecutive as reality...