Things have been very rocky between my boyfriend and I for more than six months now, and I would appreciate any advice from people who have been in similar situations that have either worked out or not worked out.

We have been in a relationship off and on for three years. A year of that was long-distance. Now we're semi-long distance -- live two hours apart and can easily see each other on the weekends, but not during the week.

We were broken up for a few months last year, and I began dating someone else. That had been going on for less than a month when my ex turned up, said that he loved me and wanted to spend his life with me. I am the first to admit that I handled the situation the worst possible way. I told my ex that I was seeing someone else and wasn't sure whether I wanted to rekindle our relationship. But I also told him that I loved him and could see myself one day marrying him (both true). I didn't intend to let things get physical, but I did, and we slept together. Then I told him I still didn't know if I wanted to get back together but that, anyway, I would break up with the other guy because I clearly wasn't ready to be in a relationship with someone else. Then, instead, I slept with the other guy one more time.

After that, I did break off the new relationship and rekindle the relationship with my ex (now my boyfriend). Things were going really well for a few months. I felt increasingly sure about the relationship and our future. I didn't tell him about the last time with the other guy, partly because I was ashamed and just wanted to forget about it, partly because I figured that it wasn't clear whether we were going to get back together when it happened, so it wasn't cheating and he didn't need to know.

Finally, several months in, I told him about it. I expected that he would be upset about it, but I didn't expect him to react as strongly as he did. He felt absolutely betrayed and disgusted and initially was going to break up with me because of it. I apologized and begged him not to leave, and we ended up reconciling , but since then, "roller coaster" doesn't begin to describe the relationship. When we're together in person, for the most part, we're loving and affectionate and enjoy each other's company. But when we're apart especially, and sometimes in person, he'll become accusing, angry, or will express self-hatred and suicidal thoughts. On a couple of occasions, he has been verbally abusive. He has never physically abused me or directly threatened me, but he has said that he has had thoughts about hurting me. On other occasions, he'll withdraw himself, partly, I know, because he wants to avoid lashing out at me. I appreciate that, but it also hurts. Sometimes he says that he doesn't think he can get over it and that he wants to end the relationship, or that he thinks I'll be happier with someone else and should leave him -- but that never lasts long.

He had depressive tendencies long before this happened, but it has definitely gotten worse. I have urged him to go to counseling, and he says he will but hasn't followed through.

As far my part in this, I do feel horrible about what I did. It was out of character for me. I went to counseling afterwards. I'm not sure how much I got out of it, to be honest, but I do know that I was confused about what I wanted and was extremely irresponsible toward myself and others in the way I handled it. I sincerely feel that I have learned my lesson -- painfully -- and won't repeat the behavior.

Sometimes my boyfriend believes that and sometimes he doesn't, but in either case, he says he just can't forget the incident and he can't help thinking about it whenever we're intimate.

I want this to work. I love him and he is my best friend, and I have no desire to be with anyone else. But I also can't live in limbo like this forever.

Any thoughts? Can we make this relationship work?