I agree with Father. I would not read too much in it. You likely just dreamed about what was on your mind before you went to sleep.
Have you ever had any other experiences that seemed to indicate that you were being called?
Regarding the habit, I cannot think of any habit that is black underneath and white on top. I understand that many Dominicans tend to wear black under their white tunic, but I don’t think it’s a requirement. Same for Trappists, I believe. Benedictine monks wear black, but not white.