Woah! lol, I'm sorry I am immature. But to be honest with you, I had a similar dream but with my grandmother. It really scared me to the point of not visiting my grandmother. I usually visit her every year around Christmas/Thanksgiving. Otherwise, I avoid. It's weird and I don't know what it means. Does it mean you are sexually attracted to your mother, or me to my grandmother?
To add another ounce of weirdness to it, I began thinking about it during the daytime when I am conscious, so... Glad to see someone else coming out with similar weird dreams, otherwise I'd keep it to myself.
But I am not sexually attracted to my grandmother or I don't think I am. Hopefully a psychologist has some answers or someone with extensive dream research experience.