I know this was posted awhile ago, but I am having similar experiences. My mother was in a relationship with someone who was terrible to me. They never actually hurt me physically, but the way they talked and acted to me were so bad that it made me wish they would just slap me around instead of treating me the way they did. My mother moved us out of the state so that she could be with them, leaving myself and my younger brother without any nearby friends or family. The longer i we stayed with this person, the worse they treated me, and i had no idea why. Over and over again, I considered running away. I only considered suicide once, but quickly pushed the thought away, knowing that I would never be able to harm myself. Still, the thought of running away was very tempting. The only thing that stopped me was that I was sure I would starve. After seven years of enduring the person's unjustified hatred of me, my mother finally moved herself, my brother, and I back to our home state.
I only added that in because it helps explain the reason that I think I am like this. And the only possible reasons are that I had either cried so much during that time that my emotions are all used up, or that I had stopped myself from crying so many times that it is now an uncontrollable reflex.
Now, even after I am separated from my former depressor, I still can't be truly happy. Unlike what you all seem to be experiencing, I am still perfectly normal around my friends and others that I know and trust. I am still able to joke and laugh around them, and most of the time, I can almost completely forget my sadness around them. At home though, I feel an unexplained sense of anger and sadness. My cold, snappy remarks start arguments that result in angering me even more. Not only have I found that I can't cry, I have also found that I can't hold a smile for more than about 10 seconds, even when I'm around friends and at my happiest. It's so bad that when I take pictures with people, they usually turn out with either my face twitching or me having a strange grimace as a result of my brain trying to make me smile while my face muscles are trying to make me frown.
My ratio of crying per year is probably about an average of less than half an hour of crying for every two years. Before I realized that there was something wrong with me that made it almost completely impossible for me to cry, I used to brag that no matter how sad or touching a movie or book was, I was the only one that never cried over it. Now, I will tears forward, and grasp at any little opportunity to make myself cry (excluding purposely causing myself physical pain), with no positive results. It seems that nothing can make me cry any more. Even the death of a loved one.
I love my pets as much as a mother loves her children. I actually do call them my sons and daughters, and treat them with so much love, I think that they also believe me to be their mother (I have never actually had any real children). First, one of my pets died. I didn't cry. Later, another of them was outside and was attacked and killed by an animal. I didn't cry. A few months later, one of them was pregnant and had her first miscarriage, giving birth to a beautiful girl who was born dead. I still didn't cry. A week later, another of my pets (who also happened to be the father of the miscarried baby) died of natural causes, even though he was still young. I couldn't cry over this either. A few months later, two of my pets got themselves lost and never showed back up again. More than six months after that, two of my 'children' died on the same night, from different causes. One from an incurable disease that she had been battling for years, and the other from coming back to the house with a broken back (we think he was hit by a car). A few weeks later, another fell ill and died. Another disappeared and has not shown back up again. Even though I love them so much that I would sacrifice my own life for theirs, I was not able to shed a single tear over any of this. Death, after death, after death, and I still couldn't cry, even when I was completely by myself.
Whenever I am sad, I will normally just get a lump in my throat and then the stinging in the back of my eyes that, for a normal person, would usually mean you are within about half a second of bursting into tears. Then, all of a sudden, it will just recede, and my feeling of despair will be replaced by a numbness. After this happens I will get extremely mad at myself for not being able to cry, and start shouting at myself in my head and punching things (pillows, my bed, the wall, etc.). On the extremely rare occasions that I do cry, I try to keep thinking about the thing that is making me cry so that I can let myself cry for as long as possible. Normally, people will see me crying and come over to try and comfort me. It usually works, and I stop crying. When this happens, I just want to scream at them: "No! Don't do that! I want to cry! Can't you just leave me alone?!
I am really not sure what could be causing this. I have looked it up online, but I can't find anything that fits. Some things I've seen suggest a severe form of depression, but I don't think it could be that because I am still happy and normal around my close friends and others that I know. Other things suggest an eye defect where a person can be born with their tear ducts blocked, but I know it can't be that because I was able to cry until my early teens. Another thing suggests a condition where a person's brain does not link tears to sadness so that the tear ducts behave much like those of an animal's and only produce tears to keep the eyes from becoming too dry. It can't be this, because the people with this disorder can still cry just like any other person can, just without their eyes watering, while I am unable to utter a single sob.