Hello
I'm so sorry that your lovely boy is going through this.
My ds, who is now 20, suffered from depression when he was 17/18. It was a very difficult time for him.and for us. He was very difficult to live with as he was also very hostile towards us. His school referred him to CAMHS but he refused to attend the appointments.
He did agree to see the GP and was prescribed anti depressants, which helped. However, he spent a period of about 9 months not functioning properly, not really getting out of bed, not seeing any friends, and I was seriously worried about him. He was also expressing suicidal thoughts and phoned the Samaritans on at least two occasions that I'm aware of.
He eventually came out of it when he left school and got a job - somthing I didn't think would happen, to be honest. I couldn't see him.being employable but in fact he was much better when working. He went to work every single day, although he had hardly ever attended school in the preceding year. He's now been working for two years, is very sociable, goes out with all his mates and is also lovely to live with.
Your ds is going through the trauma of a broken relationship, which at 16 probably seems like the end of the road. I think all you can do is be there for him, and try to reassure him that it will be ok. He probably won't believe you though. I would also stronly advocate getting support from CAMHS. Although my ds wouldn't go I've got friends whose children have benefitted from it.
Good luck