I hit my head in the summer of 2013. Up to now I've only had this feeling about 4 times of severe dizziness and a sense of dread. What could it be?

Go MD for eval. Symptoms depend on the type of head injury. Some severe symptoms may not appear right away. Mild head injury symptoms include: inability to stand or balance confusion headache nausea temporary memory loss ringing in the ear severe head injury symptoms include: bleeding from deep cuts or wounds in the scalp, loss of consciousness abnormal eye movements inability to focus the eyes.