Silent crying

Hi My son has recently started crying silently whilst loudly proclaiming 'happy - I'm happy' - he has difficulty verbalising feelings or explanations and indeed becomes more distressed if we try to talk to him about what we think is triggering the sadness - he tends to have tears streaming down his face - sometimes with his mouth open in a silent scream type expression but then if we approach him will shout 'No -Im happy' - he can have been giggling and laughing with us about something (very happy and silly sense of humour normally) only moments before. Its heartbreaking but I don't know how to help him. He reads really well - we have tried writing things down, social stories, deep pressure but no progress so far. He is 11 1/2 so puberty may be something to do with it but his emotional resilience has disappeared. Small changes are now causing days of this behaviour whereas previously that kind of thing did not bother him. ANy ideas or anyone experienced anything similar? We currently just try and focus on the things we know make him really happy and give small highlights / treats as we go along to give him things to focus on. I (his mum) am going through a depression/anxiety episode which I now very much keep away from him but I am sure this is related.