I would usually post in Behaviour or SN, but would like as many responses as possible, as I am truly at a loss as to what to do now 
My 5 yr old DS told me last night that he 'doesn't want to be in the world anymore' would 'prefer dying to another episode of living', 'wishes he was dead' and feels that he is 'naughty', 'a bad person', 'dirty' and 'hates his skin' (he is mixed race).
This has come after a weekend of being a bit down and grouchy, and a day off school (he had a very bad tongue ulcer, which the doctor thought might be a symptom of anxiety), but I absolutely do not know what prompted such an extreme reaction from him - it was a normal day, really, until he came out with this at bedtime when I was tucking him in.
I am devastated and worried sick about my poor boy.
A bit of background:
He was diagnosed with Asperger's Syndrome earlier this year. It was the culmination of a a couple of years of him just not getting on well at nursery, and then totally not coping with reception. His behaviour towards the end of summer term became so extreme (violent outbursts, inability to join in with any group stuff) that he was being frequently excluded and we were worried sick about him.
I managed - with a lot of effort (as any parent of a child with SN will understand) - to secure a pretty comprehensive, well quantified/specified statement of SEN for him, and secured him a place in a specialist provision for kids with social communication issues in a lovely mainstream primary school in our borough.
So far, so good. He has taken to his new school quite well (happy to go in the morning; engaging much better than he was in last school, although does miss old school and 'friends' very much; seems more relaxed when he comes home in the afternoon). The staff are also lovely and have a much better understanding of his issues.
At home, he has jealousy issues with his younger sister and can be quite a stroppy, willful child, but on the whole we are a very close and happy family. Me and DH are a solid couple, and he has a good male role model in his father - hard working, loving, devoted. I am a full time student, but duck and dive in order to be around for the kids. DH is self employed and works flexibly, so also puts in time doing nice stuff with the kids. My mum and sister live locally, and and spend lots of time with DS and are very devoted to him.
Also, we live in a multi-cultural environment, with lots of friends and neighbours of different backgrounds, although it is true that DS does see a lot more of his white relatives because they live closer. We have tried to instill a sense of pride in him about being mixed race, brought nice books and talked about it whenever it comes up, as honestly and positively as we can (DH black, me white by the way).
I know that my boy is an anxious, highly strung child, also very bright and thinks things over a lot, but I had no idea this is how my beautiful, lovely and much loved boy was feeling inside, and it has knocked both me and DH for six.
We tried to reassure him that he is beautiful, that he is loved and there are so many wonderful, positive things about him (managed to cheer him up a little bit by listing all the things I love about him, and all the people who love him), but it was getting late and he needed to be getting to sleep, so have left it there.
I am gutted. When he was talking he sounded like a child who is being abuse or neglected, or has suffered some sort of awful life, not the lovingly brought up, much loved little boy we know.
Please, please help. What should I do?