I have a vivid "memory" of having had sex with a good friend. Someone I loved. The only thing is in the "memory" I was wearing shoes that I hadn't worn in years. I wouldn't have had those shoes on during the period of time I believed I was intimate with my friend. My t said to me once, if there is something in the "memory/dream" that is out of place or couldn't have been there at the time you believe the event happened, it was most likely a vivid dream. I believe her and it's still a vivid memory/dream but I chalk it up to being a dream because the shoes I was wearing were from a decade prior. Basically what my t was saying is if something is out of place and time in the "memory" there is a good chance it is actually a vivid dream. I don't know if this helps you. To this day I still feel as though I made love to him. Very vivid dream.