Can you honestly say you are in love with this man or do you just love him? I think if you were in love you would know it and not even have to question.
Your ex is occupying your thoughts during the day therefore those thoughts also encroach on your sleep. Perhaps you should try occupying yourself with some sort of activity (physical may be good) to help yourself stop thinking about him in the day. I do believe the less you think of him in the day they less you will dream of him at night.
Another thing you may try is writting your dreams down when you first wake so you can analyze them. There are some great dream dictionaries both in book and online resources that can help you deciefer the meaning. Sometimes the smallest things in a dream have the biggest importance.
One more thing to try, I dont know if this will work for you or not, but I guess trying would not be so bad. Write all of your concerns, issues, worries, thoughts, feelings about your ex till you have exhausted all and can think of no more. Then, hold yourself a little ceremony, a sort of cleansing of your spirit where you take all those thoughts you wrote and burn them in the fireplace or burnbarrel (a safe way of doing this of course) if you do not have any of that, tearing it all into small pieces and repeatedly flushing may work too : ) During this ceremony imagine all thoughts, doubts, feelings etc of him going away as the paper burns or is drowned. I dont know but you may find this as a kind of theraputic release, a cleansing of the soul.
I do not think you can allow your new husband into your heart and even recognize if you do love him until you let the other one go completely.
Good luck, I hope you find your answers.