>>1
You suffer from the Emo disease. You have been unable to cope with the many difficulties in life such as being told "You are fat." This leads to sudden outbursts of laughter to try and fool yourself into believing that life and pain is actually "funny." Other times however it manifests itself in spurts of anger when you feel like breaking something in retaliation to the hurt you feel inside.
They all stem from the same source, whether it be a repeated insult you've heard many times, especially when you were a child, a self-imposed feeling of guilt over your flaws or circumstance in life, or chemicals in your brain not being properly balanced.
Seek medical help to determine if it's the last one, and if it's not, just wait a few years until you grow up. Life will kick you hard enough so that you either rise above the pain and kick back, or bury the feelings and become an asshole like everyone else. Treating your girlfriend like shit and beating your wife has become mostly acceptable as an outlet for these feelings you have. Everybody else does it.