I think it's pretty obvious: You're still in love with your ex and wish that they still loved you, too. The fact that this other girl is in the dream also suggests that you want him to choose you over anyone else, not just be in love with you.
Me and my ex have been talking after our break up. He started talking to some girl 2 weeks ago. I had a dream where we were talking and I was like "you have a girlfriend.." and he was like "I don't love her. I love you." What does this mean?
Chances are your subconscience is warning you beware of this guy as you are about to become part of a love triangle where all lose in the end. If he has already moved on then you need to do the same and don't look back. Move on and forget him but unfortunately none of us can ever see what the future holds for us but you definitely can do better than this guy. Good luck
Like astrology..don't believe in dreams
It's your subconcious' wishful thinking .. Not reality.