Ah! That's my wife's ascendant, Cancer.
Let me guess: you already guard your emotions from becoming too publicly exposed; it isn't that you never share or expose them but it must be when you are ready and comfortable, which is rather seldom. The Cancer counterpart hungers for more open exchange, and sometimes tries to probe or push or coerce, which causes the opposite response, causes you to retract and back off, and put up a defensive posture. Tension is heightened.
I saw this an automatically can relate 200% to this. This happens to me almost daily with someone I know and close with.
My boyfriend a Cancer (Cancer Moon, Leo Rising) is still having a hard time not understanding my need to not be so open. He gets upset when I come days later, after mulling things over, to tell him what was wrong or what may have upset me or pushed my buttons. He rather I do it right then and there. But I can't. It's just a reflex I have to think things over and not get so emotional about it all.
I don't like being pushed to say how i'm feeling. If I want to, I will. It's that simple.
I recently just had this problem with my boyfriend on sunday. He was asking "what's wrong?" a few times and I said nothing. I was half the time thinking about stuff and the other half literally zoning out because I was so exhausted from Hurricane Irene and running on 3hrs of sleep. He then started freaking out told me "say something!" in this tone that made me retract even further. I think once he realized, 5 minutes of even more silence, that he knew I wouldn't budge and that getting emotional about it isn't worth it.
For the most part, I think astrologically, people with certain signs in their chart that point to open eagerness to express emotionally have a hard time with anyone having a Scorpio Moon.
Scorpio Sun and Risings are more adept at expressing, even if it's just anger, they are good at just expressing it.
We on the other hand, just can't do it. It's not in our DNA of the moon sign we were born with nor will it ever be.
I think it has to also do with experience over time with being burned by people who smothered us or who spilled a secret that was too close to use that we shared in confidence or that we said something true and pure from our heart only to have it spat back in our face.
We learned at a young age at how much we can take and how much we are willing to let others feel when we do express. We are intense beings and being in our heads is no different. It's deep, dark, and still; like that of a big quiet lake at night.