Middlesex

In life we have our friends. When we get really close, sometimes our friends can feel a little bit like family. We check on them, hurt when they hurt, tell them we love them etc. Often times a deep friendship will cross over the line and become an intimate relationship. Something with a title, commitment, trust, and I suppose something to live up to. But what about that in between space?
Is there a hole with nothing in it between a friendship and a boyfriend/girlfriend relationship? If so...how do you know if that's where you are with someone, or if that is even an alright place for you to be?
Last year I had something like this with someone. I didn't know what to call it, so I didn't call it anything. I later discovered that this was probably a giant mistake, because we didn't feel the same way about each other. Maybe it's because I was married and afraid to put a title to another relationship...even if he was aware and involved in the evolution of this friendship. Perhaps it was because I sensed that maybe she wasn't really prepared to put a title to it. In any case it was different than just a friendship.
I think I want to call this place middlesex. It's kinda like that if you think about it. It isn't a friendship anymore, cause there's something making it more intimate. Maybe that "thing" is sex, or simply sexual tension...or maybe it's gotten "sexual" but there hasn't been any sex. In any case this place is complicated to say the least.