You can't diagnose yourself. As someone else said you would probably be more predisposed to it if you have a family history of schizophrenia.

The reason you cannot self diagnose it is that schizophrenia is characterised by extreme paranoia and delusions that others are plotting against you. If this was happening you can't diagnose whether your paranoia is a healthy amount or disproportionate to reality.

If you are seriously concerned then visit a psychiatrist or at least try and check the DSM-IV for schizophrenia to see if the symptoms match up.

Actually I just remembered a simple test that might give some indication. Have someone move an object such as a pen in front of your vision. Try not to focus on, or follow the pen. People with schizophrenia often struggle not to follow a moving object due to hyperactivity caused by excess dopamine.

From your description, it doesn't sound like you're schizophrenic. If you're really that worried get checked out for peace of mind.