Hi.
I can understand why you're afraid. The word "abusive" may not come to mind when you think of your relationship with D, but trying to limit your friends and using threats of suicide to control your behavior is exactly that. As adolescent psychiatrist Dr. Frederyka Shabry notes, "Most teens associate abusive behavior with physical violence, but the consequences of emotional abuse can be just as frightening." Things like insulting or cursing at a partner, destroying her property, reading her personal letters or diaries, threatening to hurt or kill her if she leaves, isolating her from friends or relatives, and trying to control the people she hangs out with are considered emotional abuse. Since abuse often escalates, I'm glad you wrote in now.
One thing in your letter made me curious. I wonder why you decided to start dating him again. Did you feel guilty for having left him? It might help to know that you bear no responsibility for his inability to move on or his desire to control you. You have an absolute right to break up and not be harassed. But Dr. Shabry suggests that the first person you may have to convince of that is yourself. Indirect ways of sending the message--like "cheating"--may actually compound your feelings of guilt and make you even more susceptible to taking him back.
It doesn't sound like this is the problem...but if you feel at all that you are in any real physical danger from D, it's important that you take steps to protect yourself. Explain your concerns to your parents or a school counselor. It may feel a bit strange to tell other people you fear D, if he hasn't actually been physically violent toward you, but people are more aware of the potential for violence since Columbine, and are more likely to take your situation seriously.
You are your own first line of defense, though. If you're afraid to break up with him in person, there are things you can do to lessen the likelihood of a confrontation. Consider breaking up with him in public, at home, with friends or relatives nearby, or even on the phone. If you do plan to break up with him in public, though, let a friend or relative know when and where. Arrange to check in with this person after you break it off--both as a safety check and as an opportunity to "debrief."
After the breakup, try not to be alone with him. If you run into him in public, do not accept rides or drinks from him. If he calls you to threaten you or to convince you to come back to him, don't take his phone calls. Just think how refreshing it will feel to be free of his control.
For more information on recognizing and dealing with abusive dating relationships, go to Making Waves, a web site designed to help teens recognize the signs of dating abuse and decide what to do about it. Or check out When Love Hurts: A Guide on Love, Respect and Abuse in Relationships.