I had almost exactly the same problem in Middle School. I was picked on so I just closed myself off from the people of who I wasn't close to and turned to reading, music, and people I met on the internet. I could feel happy and such, but I closed myself off from crying even in my own company. I taught myself to be level headed and not to show that I'm angry besides the occassional snap at people who annoy me. I learned the easiest way to not get picked on is to just to keep a low profile and confide in only your closest friends, or just not confide in anyone at all. I don't know exactly when this happened, but I do know I was in Middle School.
Eventually, though, this progressed into small self esteem problems, an inability to open up easily, problems with holding up my end of a significant conversation if it wasn't a person who I trusted, and problems with eye contact at times. I also ended up a bit of a recluse, I started smoking cigarettes, and suffered a mean depression which led to about a month of cutting in the beginning of the school year. I'm a freshman now and I am starting to fight these undesireable effects of that thought process. I hope that I'm doing a good job, but I really don't know. I just wish people in high school weren't so immature, but that's life I guess. I just want to punch my classmates occassionally.
The thing I hate about High School and Middle School is that the kids pick on anyone who is different. I fit into this category myself because of wearing a lot of black everyday and just being in a different mindset then most of them. I'm just lucky that I kind of go ignored as the shadow at the back of class, I guess, because some of my classmates are relentlessly picked on.