Why did you break up with your ex-boyfriend in the first place? Do you have evidence that he has changed? Since you're engaged to be married to someone else, what did you see in your fiancée that led you to want to spend the rest of your life with him? Obviously, there must be something there. (Is it still there?)

Can you honestly say about either one of these men that there is no one else you would rather be committed to for life? You need to answer that question without reservation before committing yourself to anyone

Right! She can't give her heart away if she doesn't know what it's saying.

. In other words, you are in no position to be marrying your fiancée if you're confused about your ex-boyfriend. You need to be really sure before you get married, because marriage is for life.  So, maybe the best thing to do is to take time away from both relationships and make sure you have completely dealt with any unresolved issues and emotions from your former relationship, and then think long-term.

Keep in mind also that when your ex-boyfriend started calling you, it probably dug up some feelings from the past. It is easy to reminisce, to think about the good times that you shared, and to romanticize the relationship while forgetting the problems or factors that led you to break up. I would recommend cutting off all contact with him for now so that you can think clearly. Sometimes those feelings come back temporarily, but they don't last, so give it some time.

On the flip side, when your ex-boyfriend discovered that you are engaged to someone else, it may have dug up his old feelings or romanticized images of your good times together. It is human nature to want something more when you can't have it, so perhaps his revived feelings are merely a result of jealousy or a sense of loss over seeing you with someone else. Be very careful; a rebound relationship like this usually doesn't last, and he may not even realize his own intentions!