How to deal with a 12yr old with zero self esteem?

[TitsalinaBumSquash]

My 12 ye old DS2 is a real worry at the moment.
He has zero self esteem and we're getting a lot of "I give up on life, what's the point of me!?" Type responses to really trivial things.

This morning it was because his breakfast fell off the plate onto the floor, he broke down over how terrible he is etc..

I honestly don't know how to deal with this anymore.
We've tried to boost him and we've had art therapy with the school and we've tried to get him with a talking therapist, he goes through periods of being selectively mute so whilst art therapy helped a bit, talking therapy didn't.

We have enrolled him in clubs and activities just for him to give him his own feeling of achievement without his siblings but it was so hard to get him to go we gave up eventually.

He's interested only on screens so that's been heavily reduced as all the adults in his life felt it was getting unhealthy (skipping meals and not socialising at school in favour of playing on his phone)

Does anyone have any advice please?
He achieves well at school and everyone says he's a dream to have around because he's usually so quiet but this constant depreciation of himself is really quite upsetting and concerning.

Ate you in the UK? Have you been through CAMHS?

My dd is on the spectrum for autism, was diagnosed at 13, now 14. She is quite negative and at 12 was talking about not wanting to live.

To some degree things have got better with time. I build on time once a month to do things with her, meal out, visit to Starbucks etc. She has various issues but we are working in our relationship and encouraging hee to see the fun in life.

We have a tv programme we watch together. I think it helps.

I talk her up a lot although I do find her hard sometimes.

No advice I'm sorry OP but I have a similar 12 year old DS. He also achieves well at school despite hating it but is very negative about himself. He can be quite clumsy and will massively overreact, call himself stupid, says there's no point. He will also call himself weird and feels he has no friends. Dreading going back to school this week.

We trying working on his self esteem by spending time together, getting out of the house, encouraging outside interests. We always try and have something to look forward to like a night away or holiday. We call this building up his whatever shield, reminding him he is loved and has things to look forward to so that when he feels like life is getting crap he can shrug it off and say "whatever" Definately doesn't always work but we take it one day / week / month at a time.

We've also bought him a book on becoming a teenager which deals a lot with hormones and self esteem and hopefully reassures him a lot of it is perfectly normal for his age.