What does it mean when you dream of your ex saying i love you?
To me, a nightmare.
On a more serious note:
Unless a dream is a recurring dream, it usually doesn't mean a thing. Dreams are the mind's way of 'filing' away all sorts of thoughts, events, feelings, memories, and emotions, as well as daily activities such as watching a tv program, reading a book, seeing a beautiful sunset, etc. The human mind processes thousands of words and thoughts and words every single day.
It could be that you thought of your ex recently, or maybe someone mentioned something about your ex and his or her name was in the back of your mind when you went to bed, even on a subconscious level.
If the dream is a recurring dream, however, it could mean you still have feelings for your ex, or it could even mean the opposite. It could also mean you still have unresolved issues with your ex. It just all depends on your particular circumstances, so if it is a recurring dream, do a bit of soul searching to try to determine if you really know what your feelings towards your ex are. And if you realize you do still have unresolved feelings or issues with him or her, then you need to deal with them in the way that's appropriate for you.