Exercise, friends and healthy diet.
It is important he spends time with people his own age. Sport is fantastic

Camhs is child and adolescent mental health service

“Mental hospital” You’d be surprised by the Mental Health Wards they are not as you imagine and no one deserves the title of mental hospital. How can you help your child when you are using titles of a stigma! You don’t want him going to a mental hospital! Come on man

Today (10th Oct) is world mental health day.
I'd get him to a gp immediately and get a referral to a psychologist. My 13yo DD was diagnosed with chronic anxiety and after a year of therapy, she is back to her beautiful, happy, bubbly self. Whatever you do, don't sweep it under the rug. He needs all of your support right now. Best of luck xx

First point of contact is usually through a GP. Depending on his age, perhaps look for a 'headspace' service in your area. Drop in and have a conversation with them and see what they can do for him and his issues.

GP and maybe ED.depending on how bad it is

First port of call would be to see your GP
There may be a many factor of things like lack of sleep, poor diet, social issues etc that are all at play at the same time. Mental Health needs to be taken very seriously but in teenagers can often be heightened by lack of routine, social media usage etc - this isn't to say that all teenagers are the same and I would never categorize mental health as it is built up from many factors and personal to the individual... Your GP can help you into the right avenues to seek help for yourself and your son. This will be a mentally and physically difficult time for yourself also so might be worth seeing a Councillor yourself.
Take each day as it comes and every step forward, no matter how small, is still a step forward.
I wish you all the luck and love it the world and I hope your son finds his happiness again x

Lots of camps and shit are available. Look for leadership and or self esteem building places.