I was in a bad car accident.. since then, I commonly feel completely different?

Nearly a year ago, (where I suffered a head injury) I was in a bad car accident.. since then, I commonly feel completely different. I often feel like a completely person than I was before the wreck. I have horrible headaches commonly, as well as a shift of attitude and mood changes. I also struggle from short term memory loss. I feel so depressed, I’ve never been like this before.