When Is It Enough?

I know that Christs' followers are supposed to "bear each other's burdens," but when is it time to realize one can not be of help any longer?

I have been conversing with this guy who possibly has borderline personality disorder for about three months now. He also has HOCD, OCD in which the sufferer is fearful that he/she might be gay. There is some good info on HOCD on the BrainPsychics website. Anyway...

It's very stressful, and it is like talking to a rebellious sixteen-year-old with the mind of a five year old (what I think a five-year-old is, anyway). This person is twenty years old. I know I probably should never have gotten into any sort of pen-pal relationship, but I can not leave it now. We're not romantically involved, though.

All I can do is to love the guy. I am not a psychiatrist or a therapist. I am only a junior in college. I have OCD myself. I just do not know what to say to this person. Lately, I have been more stern with him, but I am still fearful of possibly pushing him over the edge. My therapist tells me that if he kills himself, it's his choice, but a part of me says I would be responsible. I have nursed this person through suicidal thoughts three times. This person cuts himself. It's difficult, especially since he just about clings to me.

I feel guilty for wanting to walk away from him, but he always talks about how he is so alone, and that everyone treats him badly. I have been more stern with him to see if he would respond to that, but from what he says, he is going to do what he wants to do when he wants to do it. I do not know where he lives, and I do not want to get personally involved to the point I actually see him in person. He has talked about being violent, and I feel very uncomfortable chatting with him.

I'm not a psychiatrist. Is there one out there, or any other professional in the field of psychology? Two others from the field have told me that it would be okay to cut off communication if I had to, and I can not stay off a certain messaging service forever. A Christian response would be of great help, too.