20 Year Old Son with Suicidal thoughts and refuses help

My 20 year old son is not coping in life. He was diagnosed with Asperger's (now known as ASD) when he was younger and was in therapy for a few years, plus was on antidepressants but has been off of them for over 2 years now. He graduated from coding school in December and is now completely lost. He spirals out of control over video games and it has been escalating where he starts throwing things punching walls, biting and hitting himself. It is not easy to watch and he refuses all types of help (I mean everything). I made him a GP appt and he cancelled it saying nothing will help him.

He has had a few good moments in the past month (started going to the gym and some good times with mates) and he says none of that matters as it always goes back to him feeling like this and he wants to commit suicide. Has told me I won't be a grandmother to his kids as he won't be here when he's 30 but also says in a few weeks it won't matter anyway. He won't even look at my husband and I when we try and talk to him and pretty much lays in his bed all day on his phone (playing more games) and then after a day or so, gets back on the video games on his computer and the cycle starts again. He works one day a week (for ~5 hours) and won't pick up more shifts.

So what can I do for someone who absolutely refuses to help themselves and will barely talk to us. I'm at my wits end and not coping. I check on him throughout the day and tell him I love him and I'm going to keep asking him if he will talk to someone because one day he might just say yes. Anyone been in this situation and have any ideas? Thank you!