DreamsMaster: Your dreaming mind is definitely trying to get your attention, based on the fact that you’ve had the dream three times and it’s making a strong emotional impact.
The first thing you want to look at is the literal context. Do you sense your boyfriend is involved in some type of dangerous activity that could result in violent action toward him? If so, the dream may be a warning, and I strongly encourage you to talk to him about it to see if he can change course.
If the literal angle doesn’t fit, then look for symbolism. For example, seeing him dead could mean that your image of him has died, that he’s no longer the person you initially thought he was. The cops or police in the dream could represent your conscience, the part of you that knows right from wrong.
Think back to what was on your mind the night(s) you had this dream. If you can’t recall, then the next time you have the dream, write it down along with what happened or what was on your mind the day or night before. Soon a trend will become clear, and you’ll know what the message is and what action you need to take.