Dreams are a funny thing. We have them for all sorts of reasons but mostly because something is on our mind. You are thinking about him and thus, he shows up in your dreams. I wouldn't put any more thought into it than that. You probably still have conflicting feelings about the way things were left and if you'll get back to gether. Thus, your subconscious thinks about it and pop---------- there he is in a dream.
I'd give him the time he needs and see what else is out there for you as well. If you meet someone, they may then start showing up in your dreams too. If you end up getting back together with your ex, so be it. Time will tell with that. For now he is saying "not now".
Break ups are hard and take time to get over. I'd try to read a good book before bed and be good and tired when you turn off the light so that you drift off straight to sleep. Keep busy so that you have less time to day dream about him and maybe it will show up less in your night dreams.
You mentioned speaking to him a lot and I would assume You would also be thinking about him quite often which would explain why You are dreaming about him.