Trigger warning: suicide, self harm, eating disorders, PTSD.

I desperately need some advice. My boyfriend is talking very seriously about suicide and says he has a plan and a date for it to happen - but refuses to tell me the date and plan. He suffers with depression, anxiety, PTSD, an eating disorder and has previously self-harmed and attempted suicide once or twice in the past. He has also been sectioned twice.

I suffer with my mental health too and have had suicidal thoughts so this is not wholly unfamiliar to me. I've tried to listen as much as I can and try to suggest things that might help but it seems like his mind is completely made up. He says he wants to say his goodbyes and has asked me to look after his dog for him.

I'm in two minds whether to blow the whistle on it and tell his mum and/or a healthcare professional about his plans. Obviously I will do anything to prevent him from going ahead with his plan, however I also don't want to break his trust. If he doesn't go ahead with his plan right now, he may not be able to trust me to tell me about his next plan, for example.

Please help. He didn't give me a timeframe for his plan, but he said 'soon'. Thanks in advance.