In your version of the CC, what does "Crossing" stand for? In my version it stands for: Whatever blocks or opposes the querent, whatever challenges must be faced
So, before we go racing into marriage, let's keep in mind the positions. The Hierophant is the querent's current position. Currently, the querent (you?) is in a traditional position; status quo, with querent and partner in traditional roles, taking traditional steps. No rushing things, no side tracking. It might even be that the relationship has some religious or cultural overtones: no pre-marital sex, no fooling around, marriage in the future rather than living together...yadda, yadda, yadda.
Hmmm. But my, oh, my. There's the Ace of Cups.
This isn't marriage, I'm afraid. This is the challenge of STAYING in a traditional relationship that might well LEAD to marriage while fighting off the challenges that love brings. Now I don't know the rest of the spread--and you might want to post it in READINGS to see if I'm right here, but I'm guessing that the relationship is facing some challenges and temptations to turn off that traditional road. Either those involved want to do something non-traditional (and this could be anything from premarital sex to kinky sex), or one partner or the other likes to look at other people and imagine having a relationship with them.
Don't fret. It's an Ace of Cups. That means that only the spark of an idea is there. The stirring of emotion. But being that it's in that position, crossing, it still indicates a challenge that must be faced, not denied or ignored.
That's how I'd read it.