Guys I really need your help.. =/?

Whenever I'm doing something, at any time of the day, I constantly get pictures in my mind of the worst that can happen in any situation; whether its simply watching someone do the dishes or me standing beside a window and suddenly picturing myself getting shot in the head. I'm constantly worrying and it's like torture in my head. I'm having difficulty returning back to reality as i'm trying to recover from a two year period of loneliness and suppressed emotions. I'm tired of having horrendous thoughts because it's starting to make me sick when I think of them and I don't even know why they pop up... :( I'm trying to enjoy life to it's fullest and remain positive but this problem is holding me back, which is why I'm at yahoo answers : ) and is seeking your help in order to stop this issue. So... Any suggestions?