What Does It Mean When A Man Says Im Not In Love With You Yet?

It means he is not in love with you yet.  However, if things continue on their course, there is a possibility that he might. (Either way, there is a lot at risk, isn't there?) Perhaps he is waiting for something or expecting something to happen.  

Kind of a mysterious thing to say, I think. Have you asked him directly about it?  If not, then why not?  Couples let too much go unsaid.  If there is ambiguity, then there are so many more chances for someone's feelings to get hurt, expectations (either fair or unfair) to not be met, the "rules" not understood (everyone brings their own rules into a relationship...everyone).

Get it out in the open and talk to him about it.

It means that he is not in love with you and you should find another man.