Teenage son self harming

pls help- my son has been under camhs for 16 months and we were told from the off he has ASD however he doesn’t know yet as advised not too. However we have an appt tomorrow where we are telling him after he had a complete melt down triggered by returning to school after the summer! Resulting him in running away the police out looking for him as he had taken tablets trying to end his life- then showing me he had cuts and burns on his legs! The last few months he has been so happy (even we questioned if he did have autism and that he was just being a normal teenage boy with raging hormones ) but he has been struggling and I had no idea.....I feel helpless