A) its just a dream
B) if you are 'afraid' of developing feeling for you ex even though you love another girl you are kidding yourself.
If you love this new girl, you would not be afraid. Its obvious you do not have closure with the previous woman and you still want her. Get over it! Get over yourself! Devote yourself to the new woman in your life or SET HER FREE. Look up the definition of DEVOTION. Do not string her along because you dont want to be alone or you are afriad of hurting her. You will hurt her much more if you continue this relationship in any other way.
Life is too short for all this drama. Be kind, Love fully and LIVE!