Can we say "wedding jitters?" I think you have a pretty good case! :)
Cars in dreams are familiar metaphors for our selves -- for the "direction we are headed" in our lives. Accordingly, when we dream of losing control of a vehicle (if the brakes or steering wheel don't work, or if have an accident) we are encouraged to look for areas where we feel out of control in our waking lives.
Clues to the origin of "out-of-control" dreams often are contained within the story lines of the dreams. In each of your dreams, for example, immediately after the car crash, you find yourself "talking to other men" -- presumably flirting -- "right in front" of your fiancé.
Given the background you have provided, is it fair to say that occasionally you wonder if you and your fiancé will reach your agreed-upon destination -- the wedding altar? The car crash suggests an interrupted trip. What's worse, as a result of these dreams, you write that you and your fiancé haven't spoken in days.
It is normal, on the eve of a wedding, for brides and grooms to get "cold feet." During this period, engaged couples often are perplexed by odd dreams. They may be reunited with ex-lovers whom they formerly worked hard to leave behind. Or, like yourself, they may dream of flirting or being romantically involved with mere acquaintances -- people who hold no realistic romantic interest. The common thread in all wedding jitters dreams is a retreat away from a frightening future, to a past that, by comparison, appears safe and inviting.
Only time will tell if your dreams indicate a genuine detour on the road to marriage, or if they signify a natural bump in the road. In either case, it is important that you share your dreams -- and the feelings of doubt and confusion that they represent -- with your fiancé. If you want to survive the long road of marriage that lies ahead of you together, you will have to learn to navigate the rough spots. You may as well get started now, to see how you fare.
The road to marriage always is a nerve-filled ride, with doubts about oneself and one's partner making frequent, ghost-like appearances in the passenger seat. What's the message of this dream? Don't be spooked by ghosts, and keep both hands firmly on the wheel.