He thinks suicide is the only solution

So, as I have mentioned before, my bf is bipolar depressed. Last night he told me that he is on antibiotics for Hodgkin's Lymphoma. He says that if he is diagnosed he will kill himself the humane way. I asked him to clarify and he said he would use an exit bag, no mess and quick. He told me he doesn't want to suffer or put his family in debt. Is it selfish of me for telling him that I don't want him to kill himself? I am falling in love with him and he told me he's falling for me. What should I do?